Mobile communication system

ABSTRACT

A closed subscriber group (CSG) cell is a cell that allows use of subscribers. In order to receive the service by the CSG cell, a CSG-ID is required to be notified to a user equipment, which cannot be obtained in a situation outside the reach of radio waves from a non-CSG cell. In a mobile communication system including base stations respectively provided to a CSG cell and a non-CSG cell in which access is made to the CSG cell with the use of a CSG-ID issued in a case where use of the CSG cell is allowed, the base station provided in the CSG cell refers to the notified identification information of a user equipment and then transmits a tracking area update request from the user equipment to a core network, and the core network determines whether the user equipment is allowed to use the CSG cell and, in the case where the use is allowed, transmits a signal for allowing assignment of radio resources to the user equipment and the CSG-ID. The user equipment accesses the CSG cell with the use of the CSG-ID.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/807,528, filed Jul. 23, 2015, which is a divisional applicationof U.S. application Ser. No. 13/127,632 filed May 4, 2011, which is theU.S. National Stage application of PCT International Application No.PCT/JP2009/005622 filed Oct. 26, 2009, which claims priority to JapaneseApplication No. 2008-283004 filed Nov. 4, 2008 and Japanese ApplicationNo. 2009-230545 filed Oct. 2, 2009. U.S. application Ser. No. 14/807,528is herein incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The present invention relates to a mobile communication system in whicha base station performs radio communications with a plurality of userequipments.

BACKGROUND ART

Commercial service of a wideband code division multiple access (W-CDMA)system among so-called third-generation communication systems has beenoffered in Japan since 2001. In addition, high speed down link packetaccess (HSDPA) service for achieving higher-speed data transmissionusing a down link has been offered by adding a channel for packettransmission (high speed-downlink shared channel (HS-DSCH)) to the downlink (dedicated data channel, dedicated control channel). Further, inorder to increase the speed of data transmission in an uplink direction,service of a high speed up link packet access (HSUPA) has been offered.W-CDMA is a communication system defined by the 3rd generationpartnership project (3GPP) that is the standard organization regardingthe mobile communication system, where the specifications of Release 8version are produced.

Further, 3GPP is investigating new communication systems referred to as“long term evolution (LTE)” regarding radio areas and “systemarchitecture evolution (SAE)” regarding the overall system configurationincluding a core network (merely referred to as network as well) ascommunication systems independent of W-CDMA. In the LTE, an accessscheme, radio channel configuration and a protocol are totally differentfrom those of the current W-CDMA (HSDPA/HSUPA). For example, as to theaccess scheme, code division multiple access is used in the W-CDMA,whereas in the LTE, orthogonal frequency division multiplexing (OFDM) isused in a downlink direction and single career frequency divisionmultiple access (SC-FDMA) is used in an uplink direction. In addition,the bandwidth is 5 MHz in the W-CDMA, while in the LTE, the bandwidthcan be selected from 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHzfor each base station. Further, differently from the W-CDMA, circuitswitching is not provided but a packet communication system is onlyprovided in the LTE.

The LTE is defined as a radio access network independent of the W-CDMAnetwork because its communication system is configured with a new corenetwork different from a core network (GPRS) of the W-CDMA. Therefore,for differentiation from the W-CDMA communication system, a base stationthat communicates with a user equipment (UE) and a radio networkcontroller that transmits/receives control data and user data to/from aplurality of base stations are referred to as an E-UTRAN NodeB (eNB) andan evolved packet core (EPC: also referred to as access gateway (aGW)),respectively, in the LTE communication system. Unicast service andevolved multimedia broadcast multicast service (E-MBMS service) areprovided in this LTE communication system. The E-MBMS service isbroadcast multimedia service, which is merely referred to as MBMS insome cases. Bulk broadcast contents such as news, weather forecast andmobile broadcast are transmitted to a plurality of UEs. This is alsoreferred to as point to multipoint service.

Non-Patent Document 1 describes the current decisions by 3GPP regardingan overall architecture in the LTE system. The overall architecture(Chapter 4 of Non-Patent Document 1) is described with reference toFIG. 1. FIG. 1 is a diagram illustrating the configuration of the LTEcommunication system. With reference to FIG. 1, the evolved universalterrestrial radio access (E-UTRAN) is composed of one or a plurality ofbase stations 102, provided that a control protocol (for example, radioresource management (RRC)) and a user plane (for example, packet dataconvergence protocol (PDCP), radio link control (RLC), medium accesscontrol (MAC), and physical layer (PHY)) for a UE 101 are terminated inthe base station 102. The base stations 102 perform scheduling andtransmission of paging signaling (also referred to as paging messages)notified from a mobility management entity (MME) 103. The base stations102 are connected to each other by means of an X2 interface. Inaddition, the base stations 102 are connected to an evolved packet core(EPC) by means of an S1 interface, more specifically, connected to themobility management entity (MME) 103 by means of an S1_MME interface andconnected to a serving gateway (S-GW) 104 by means of an S1_U interface.The MME 103 distributes the paging signaling to multiple or a singlebase station 102. In addition, the MME 103 performs mobility control ofan idle state. When the UE is in the idle state and an active state, theMME 103 manages a list of tracking areas. The S-GW 104transmits/receives user data to/from one or a plurality of base stations102. The S-GW 104 serves as a local mobility anchor point in handoverbetween base stations. Moreover, there is provided a PDN gateway (P-GW),which performs per-user packet filtering and UE-ID address allocation.

The current decisions by 3GPP regarding the frame configuration in theLTE system are described in Non-Patent Document 1 (Chapter 5), which aredescribed with reference to FIG. 2. FIG. 2 is a diagram illustrating theconfiguration of a radio frame used in the LTE communication system.With reference to FIG. 2, one radio frame is 10 ms. The radio frame isdivided into ten equally sized subframes. The subframe is divided intotwo equally sized slots. The first (#0) and sixth (#5) subframes containa downlink synchronization signal (SS) per each frame. Thesynchronization signals are classified into a primary synchronizationsignal (P-SS) and a secondary synchronization signal (S-SS).Multiplexing of channels for multimedia broadcast multicast servicesingle frequency network (MBSFN) and for non-MBSFN is performed on aper-subframe basis. Hereinafter, a subframe for MBSFN transmission isreferred to as an MBSFN subframe. Non-Patent Document 2 describes asignaling example when MBSFN subframes are allocated. FIG. 3 is adiagram illustrating the configuration of the MBSFN frame. Withreference to FIG. 3, the MBSFN subframes are allocated for each MBSFNframe. An MBSFN frame cluster is scheduled. A repetition period of theMBSFN frame cluster is allocated.

Non-Patent Document 1 describes the current decisions by 3GPP regardingthe channel configuration in the LTE system. It is assumed that the samechannel configuration is used in a closed subscriber group (CSG) cell asthat of a non-CSG cell. A physical channel (Chapter 5 of Non-PatentDocument 1) is described with reference to FIG. 4. FIG. 4 is a diagramillustrating physical channels used in the LTE communication system.With reference to FIG. 4, a physical broadcast channel (PBCH) 401 is adownlink channel transmitted from the base station 102 to the UE 101. ABCH transport block is mapped to four subframes within a 40 ms interval.There is no explicit signaling indicating 40 ms timing. A physicalcontrol format indicator channel (PCFICH) 402 is transmitted from thebase station 102 to the UE 101. The PCFICH notifies the number of OFDMsymbols used for PDCCHs from the base station 102 to the UE 101. ThePCFICH is transmitted in each subframe. A physical downlink controlchannel (PDCCH) 403 is a downlink channel transmitted from the basestation 102 to the UE 101. The PDCCH notifies the resource allocation,HARQ information related to DL-SCH (downlink shared channel that is oneof the transport channels shown in FIG. 5A) and the PCH (paging channelthat is one of the transport channels shown in FIG. 5A). The PDCCHcarries an uplink scheduling grant. The PDCCH carries ACK/Nack that is aresponse signal to uplink transmission. The PDCCH is referred to as anL1/L2 control signal as well. A physical downlink shared channel (PDSCH)404 is a downlink channel transmitted from the base station 102 to theUE 101. A DL-SCH (downlink shared channel) that is a transport channeland a PCH that is a transport channel are mapped to the PDSCH. Aphysical multicast channel (PMCH) 405 is a downlink channel transmittedfrom the base station 102 to the UE 101. A multicast channel (MCH) thatis a transport channel is mapped to the PMCH.

A physical uplink control channel (PUCCH) 406 is an uplink channeltransmitted from the UE 101 to the base station 102. The PUCCH carriesACK/Nack that is a response signal to downlink transmission. The PUCCHcarries a channel quality indicator (CQI) report. The CQI is qualityinformation indicating the quality of received data or channel quality.In addition, the PUCCH carries a scheduling request (SR). A physicaluplink shared channel (PUSCH) 407 is an uplink channel transmitted fromthe UE 101 to the base station 102. A UL-SCH (uplink shared channel thatis one of the transport channels shown in FIG. 5B) is mapped to thePUSCH. A physical hybrid ARQ indicator channel (PHICH) 408 is a downlinkchannel transmitted from the base station 102 to the UE 101. The PHICHcarries ACK/Nack that is a response to an uplink transmission. Aphysical random access channel (PRACH) 409 is an uplink channeltransmitted from the UE 101 to the base station 102. The PRACH carries arandom access preamble.

At downlink reference signal which is a known symbol in a mobilecommunication system is inserted in the first, third and last OFDMsymbols of each slot. The physical layer measurement objects of a UEincludes, for example, reference symbol received power (RSRP).

The transport channel (Chapter 5 of Non-Patent Document 1) is describedwith reference to FIGS. 5A and 5B. FIGS. 5A and 5B are diagramsillustrating transport channels used in the LTE communication system.FIG. 5A shows mapping between a downlink transport channel and adownlink physical channel. FIG. 5B shows mapping between an uplinktransport channel and an uplink physical channel. A broadcast channel(BCH) is broadcast to the entire base station (cell) regarding thedownlink transport channel. The BCH is mapped to the PBCH.Retransmission control according to a hybrid ARQ (HARQ) is applied to adownlink shared channel (DL-SCH). Broadcast to the entire base station(cell) is enabled. The DL-SCH supports dynamic or semi-static resourceallocation. The semi-static resource allocation is also referred to aspersistent scheduling. The DL-SCH supports discontinuous reception (DRX)of a UE for enabling the UE to save power. The DL-SCH is mapped to thePDSCH. The paging channel (PCH) supports DRX of the UE for enabling theUE to save power. Broadcast to the entire base station (cell) isrequired. The PCH is mapped to physical resources such as the PDSCH thatcan be used dynamically for traffic or physical resources such as thePDCCH of the other control channel. The multicast channel (MCH) is usedfor broadcast to the entire base station (cell). The MCH supports SFNcombining of MBMS service (MTCH and MCCH) in multi-cell transmission.The MCH supports semi-static resource allocation. The MCH is mapped tothe PMCH.

Retransmission control according to a hybrid ARQ (HARQ) is applied to anuplink shared channel (UL-SCH). The UL-SCH supports dynamic orsemi-static resource allocation. The UL-SCH is mapped to the PUSCH. Arandom access channel (RACH) shown in FIG. 5B is limited to controlinformation. There is a collision risk. The RACH is mapped to the PRACH.The HARQ is described.

The HARQ is the technique for improving the communication quality of achannel by combination of automatic repeat request and forward errorcorrection. The HARQ has an advantage that error correction functionseffectively by retransmission even for a channel whose communicationquality changes. In particular, it is also possible to achieve furtherquality improvement in retransmission through combination of thereception results of the first transmission and the reception results ofthe retransmission. An example of the retransmission method isdescribed. In a case where the receiver fails to successfully decode thereceived data (in a case where a cyclic redundancy check (CRC) erroroccurs (CRC=NG)), the receiver transmits “Nack” to the transmitter. Thetransmitter that has received “Nack” retransmits the data. In a casewhere the receiver successfully decodes the received data (in a casewhere a CRC error does not occur (CRC=OK)), the receiver transmits “AcK”to the transmitter. The transmitter that has received “Ack” transmitsthe next data. Examples of the HARQ system includes “chase combining”.In chase combining, the same data sequence is transmitted in the firsttransmission and retransmission, which is the system for improving gainsby combining the data sequence of the first transmission and the datasequence of the retransmission. This is based on the idea that correctdata is partially included even if the data of the first transmissioncontains an error, and highly accurate data transmission is enabled bycombining the correct portion of the first transmission data and theretransmission data. Another example of the HARQ system is incrementalredundancy (IR). The IR is aimed to increase redundancy, where a paritybit is transmitted in retransmission to increase the redundancy bycombining the first transmission and retransmission, to thereby improvethe quality by an error correction function.

A logical channel (Chapter 6 of Non-Patent Document 1) is described withreference to FIGS. 6A and 6B. FIGS. 6A and 6B are diagrams illustratinglogical channels used in an LTE communication system. FIG. 6A showsmapping between a downlink logical channel and a downlink transportchannel. FIG. 6B shows mapping between an uplink logical channel and anuplink transport channel. A broadcast control channel (BCCH) is adownlink channel for broadcast system control information. The BCCH thatis a logical channel is mapped to the BCH or DL-SCH that is a transportchannel. A paging control channel (PCCH) is a downlink channel fortransmitting paging signals. The PCCH is used when the network does notknow the cell location of a UE. The PCCH that is a logical channel ismapped to the PCH that is a transport channel. A common control channel(CCCH) is a channel for transmission control information between UEs anda base station. The CCCH is used in a case where the UEs have no RRCconnection with the base station. In downlink, the CCCH is mapped to theDL-SCH that is a transport channel. In uplink, the CCCH is mapped to theUL-SCH that is a transport channel.

A multicast control channel (MCCH) is a downlink channel forpoint-to-multipoint transmission. The MCCH is a channel used fortransmitting MBMS control information for one or several MTCHs. The MCCHis a channel used only by a UE during reception of the MBMS. The MCCH ismapped to the DL-SCH or MCH that is a transport channel. A dedicatedcontrol channel (DCCH) is a channel that transmits dedicated controlinformation between a UE and a network. The DCCH is mapped to the UL-SCHin uplink and mapped to the DL-SCH in downlink. A dedicated trafficchannel (DTCH) is a point-to-point communication channel fortransmission of user information to a dedicated UE. The DTCH exists inuplink as well as downlink. The DTCH is mapped to the UL-SCH in uplinkand mapped to the DL-SCH in downlink. A multicast traffic channel (MTCH)is a downlink channel for traffic data transmission from a network to aUE. The MTCH is a channel used only by a UE during reception of theMBMS. The MTCH is mapped to the DL-SCH or MCH.

GCI represents a global cell identity. A closed subscriber group (CSG)cell is introduced in the LTE and universal mobile telecommunicationsystem (UMTS). The CSG is described below (Chapter 3.1 of Non-PatentDocument 7). The closed subscriber group (CSG) is a cell in whichavailable subscribers are identified by an operator (cell for identifiedsubscribers). The identified subscribers are authorized to access one ormore E-UTRAN cells of a public land mobile network (PLMN). One or moreE-UTRAN cells in which the identified subscribers are permitted accessare referred to as “CSG cell(s)”. Note that access is limited in thePLMN. The CSG cell is part of the PLMN that broadcasts a specific CSGidentity (CSG ID, CSG-ID). The authorized members of the subscribergroup who have registered in advance access the CSG cells using theCSG-ID that is the access enabling information. The CSG-ID is broadcastby the CSG cell or cells. A plurality of CSG-IDs exist in a mobilecommunication system. The CSG-IDs are used by UEs for facilitatingaccess from CSG-related members. 3GPP discusses in a meeting that theinformation to be broadcast by the CSG cell or cells is changed from theCSG-ID to a tracking area code (TAC). The locations of UEs are tracedbased on an area composed of one or more cells. The locations are tracedfor enabling tracing of the locations of UEs and calling (calling ofUEs) even in the state where communication is not performed (in an idlestate). An area for tracing locations of UEs is referred to as atracking area. A CSG whitelist is a list stored in the USIM containingall the CSG IDs of the CSG cells to which the subscribers belong. Thewhitelist of the UE is provided by a higher layer. By means of this, thebase station of the CSG cell allocates radio resources to the UEs.

A “suitable cell” is described below (Chapter 4.3 of Non-Patent Document7). The “suitable cell” is a cell on which a UE camps on to obtainnormal service. Such a cell shall fulfill the following: (1) the cell ispart of the selected PLMN or the registered PLMN, or part of the PLMN ofan “equivalent PLMN list”; and (2) according to the latest informationprovided by a non-access stratum (NAS), the cell shall further fulfillthe following conditions: (a) the cell is not a barred cell; (b) thecell is part of at least one tracking area (TA), not part of “forbiddenLAs for roaming”, where the cell needs to fulfill (1) above; (c) thecell fulfills the cell selection criteria; and (d) for a cell identifiedas CSG cell by system information (SI), the CSG-ID is part of a “CSGwhitelist” of the UE (contained in the CSG whitelist of the UE).

An “acceptable cell” is described below (Chapter 4.3 of Non-PatentDocument 7). This is the cell on which a UE camps to obtain limitedservice (emergency calls). Such a cell shall fulfill all the followingrequirements. That is, the minimum required set for initiating anemergency call in an E-UTRAN network are as follows: (1) the cell is nota barred cell; and (2) the cell fulfills the cell selection criteria.

Camping on a cell represents the state where a UE has completed the cellselection/reselection process and the UE has chosen a cell formonitoring the system information and paging information.

PRIOR ART DOCUMENTS Non-Patent Documents

Non-Patent Document 1: 3GPP TS36.300 V8.6.0

Non-Patent Document 2: 3GPP R1-072963

Non-Patent Document 3: 3GPP TR R3.020 V0.6.0

Non-Patent Document 4: 3GPP R2-082899

Non-Patent Document 5: 3GPP R2-083494

Non-Patent Document 6: 3GPP TS36.331 V8.3.0

Non-Patent Document 7: 3GPP TS36.304 V8.3.0

Non-Patent Document 8: 3GPP R2-084346

Non-Patent Document 9: 3GPP S1-083461

Non-Patent Document 10: 3GPP R2-093950

Non-Patent Document 11: 3GPP R2-093864

Non-Patent Document 12: 3GPP R2-093138

Non-Patent Document 13: 3GPP TS36.213

Non-Patent Document 14: 3GPP TS36.101

SUMMARY OF INVENTION Problems to be Solved by the Invention

It is required to install a large number of closed subscriber group(CSG) cells in apartment buildings, schools, companies and the like. Forexample, the CSG cells are required to be installed for each room inapartment buildings, for each classroom in schools, and for each sectionin companies in such a manner that only users who have registered therespective CSG cells are allowed to use those CSG cells. Further, theCSG cells are assumed to have portable size and weight, and those CSGcells are also required to be installed or removed frequently andflexibly. Considering the above-mentioned demands, radio waves from alarge number of CSG cells are simultaneously transmitted in onelocation. That is, a situation in which UEs are located in the positionswithin the reach of the radio waves from a large number of CSG cellsoccurs in apartment buildings, schools, companies and the like.

Alternatively, the CSG cells are required to be installed in the placesoutside the reach of the radio waves from non-CSG cells for enablingcommunication with UEs through the CSG cells. Currently, for example,rooms in apartment buildings are outside the reach of the radio wavesfrom non-CSG cells in many cases. In such cases, the CSG cells areinstalled for each room of apartment buildings, and the CSG is composedof the CSG cells for each room to be provided with a CSG-ID. Forexample, a case where user access registration of a UE of a resident ineach room is performed for the CSG cell of each room is conceivable. Insuch a situation, the UE is located in a place outside the reach of theradio waves from non-CSG cells but within the reach of the radio wavesfrom a large number of CSG cells. Further, in such a case, depending onan environment where radio waves propagate, the radio wave from the CSGcell with which user access registration has been performed does notreach the UE, or even if it reaches the UE, the received power issmaller compared with other CSG cells in many cases.

As described above, in the case of a UE located in a position within thereach of the radio waves from a large number of CSG cells, there occursa situation in which search and cell selection are endlessly repeatedfor numbers of CSG cells that cannot be accessed (that is, CSG cellswith which user access registration has not been performed). Such a caseleads to a control delay in a system and reductions in radio resourceutilization efficiency and signaling efficiency. Moreover, there arisesa problem of an increase in power consumption of a UE that repeats cellsearch. Assuming a future situation in which the CSG cells are arrangedas described above, those problems become crucial ones. The presentinvention has been made to solve those problems.

Means to Solve the Problems

A mobile communication system according to the present inventionincludes user equipments, base stations and a radio network controller,the user equipments performing data transmission/reception using anorthogonal frequency division multiplexing (OFDM) system as a downlinkaccess system and a single career frequency division multiple access(SC-FDMA) system as an uplink access system, the base stations providedrespectively to cells for specific subscribers that are open only tospecific ones of the user equipments or subscribers and cells fornon-specific users that are allowed to be used by non-specific ones ofthe user equipments or users and executing scheduling of assignment ofradio resources to the user equipments, the radio network controllermanaging a desired tracking area in which the user equipments arelocated through a plurality of the base stations and performing pagingon the user equipments, in which the user equipments access the cellsfor specific subscribers using access allowance information issued uponuse of the cells for specific subscribers being allowed, wherein: thebase stations provided to the cells for specific subscribers refer toidentification information of the user equipments notified by the radionetwork controller and transmit a tracking area update request for theradio network controller from the user equipments to the radio networkcontroller; the radio network controller determines whether the userequipments that have transmitted the tracking area update request areallowed to use the cells for specific subscribers, and in a case wherethe use is allowed, transmits a signal for allowing the assignment ofradio resources to the user equipments and the access allowanceinformation to the base stations provided to the cells for specificsubscribers; and the user equipments access the base stations providedto the cells for specific subscribers using the access allowanceinformation received from the base stations provided to the cells forspecific subscribers.

Effects of the Invention

The mobile communication system according to the present inventionincludes user equipments, base stations and a radio network controller,the user equipments performing data transmission/reception using anorthogonal frequency division multiplexing (OFDM) system as a downlinkaccess system and a single career frequency division multiple access(SC-FDMA) system as an uplink access system, the base stations providedrespectively to cells for specific subscribers that are open only tospecific ones of the user equipments or subscribers and cells fornon-specific users that are allowed to be used by non-specific ones ofthe user equipments or users and executing scheduling of assignment ofradio resources to the user equipments, the radio network controllermanaging a desired tracking area in which the user equipments arelocated through a plurality of the base stations and performing pagingon the user equipments, in which the user equipments access the cellsfor specific subscribers using access allowance information issued uponuse of the cells for specific subscribers being allowed, wherein: thebase stations provided to the cells for specific subscribers refer toidentification information of the user equipments notified by the radionetwork controller and transmit a tracking area update request for theradio network controller from the user equipments to the radio networkcontroller; the radio network controller determines whether the userequipments that have transmitted the tracking area update request areallowed to use the cells for specific subscribers, and in a case wherethe use is allowed, transmits a signal for allowing the assignment ofradio resources to the user equipments and the access allowanceinformation to the base stations provided to the cells for specificsubscribers; and the user equipments access the base stations providedto the cells for specific subscribers using the access allowanceinformation received from the base stations provided to the cells forspecific subscribers. Accordingly, even in a state of being not notifiedthe whitelist (access allowance information), the UE can update thetracking area for the radio network controller (core network, MME) andobtain the whitelist from the core network via the CSG cell (cell forspecific equipments).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the configuration of an LTEcommunication system.

FIG. 2 is a diagram illustrating the configuration of a radio frame usedin the LTE communication system.

FIG. 3 is a diagram illustrating the configuration of a multimediabroadcast service single frequency network (MBSFN) frame.

FIG. 4 is a diagram illustrating physical channels used in the LTEcommunication system.

FIGS. 5A and 5B are diagrams illustrating transport channels used in theLTE communication system.

FIGS. 6A and 6B are diagrams illustrating logical channels used in theLTE communication system.

FIGS. 7A and 7B are block diagrams showing the overall configuration ofa mobile communication system currently under discussion of 3GPP.

FIG. 8 is a block diagram showing the configuration of a UE 71 accordingto the present invention.

FIG. 9 is a block diagram showing the configuration of a base station 72according to the present invention.

FIG. 10 is a block diagram showing the configuration of an MME accordingto the present invention.

FIG. 11 is a block diagram showing the configuration of a HeNBGWaccording to the present invention.

FIG. 12 is a flowchart schematically showing cell search performed by auser equipment (UE) in the LTE communication system.

FIG. 13 is a conceptual diagram in a case where a large number of CSGcells exist.

FIG. 14 is a flowchart of cell search of a UE located in a positionwithin the reach of radio waves from a large number of Home-eNBs.

FIG. 15 is a sequence diagram for broadcasting PCI split informationaccording to a first embodiment.

FIG. 16 is a flowchart of cell search of a UE according to the firstembodiment.

FIG. 17 is a sequence diagram for broadcasting PCI split informationaccording to a first modified example of the first embodiment.

FIG. 18 is a sequence diagram for broadcasting PCI split information onthe other frequency layer.

FIG. 19 is a diagram showing a case where a Home-eNB is located withinan eNB area.

FIG. 20 is a sequence diagram of a method of notifying a whitelistthrough a non-CSG cell, which is under discussion of 3GPP.

FIG. 21 is a diagram showing a case where a Home-eNB (CSG cell) withwhich a UE has registered is out of a non-CSG cell area.

FIG. 22 is a sequence diagram in a case where a UE that does not have awhitelist according to a third embodiment starts manual search.

FIG. 23 is a diagram showing a case where a UE is being served by aplurality of CSG cells not by a non-CSG cell.

FIG. 24 is a sequence diagram in a case where manual search according toa fourth embodiment is performed.

FIG. 25 is a sequence diagram of a method of transmitting a whitelistmessage before transmitting TAU reject.

FIG. 26 is a sequence diagram of a method disclosed in a first modifiedexample of a fifth embodiment.

FIG. 27 is a sequence diagram of a method of prohibiting, in a case ofreceiving a TAU reject message from the same cell, RRC connectionestablishment with the cell by a UE.

FIG. 28 is a diagram showing the process by a UE in a case where a timeris provided.

FIG. 29 is a sequence diagram of a method of transmitting a registeredmessage of a whitelist before transmitting an n-th TAU reject messageaccording to a seventh embodiment.

FIG. 30 is a sequence diagram of a method of prohibiting, in a casewhere one RRC connection reject message is received from the same cell,RRC connection request for the cell by a UE.

FIG. 31 is a sequence diagram of a method of transmitting, by a UE, aregistered message of a whitelist before a CSG cell belonging to aCSG-ID in which user access registration has not been performedtransmits an RRC connection reject message.

FIG. 32 is a sequence diagram of a method of sending Ack/Nack indicatingsuccess/failure of (updated) whitelist message reception according to aneleventh embodiment.

FIG. 33 is a flowchart showing the process of a UE regarding RRCconnection re-establishment.

FIG. 34 is a flowchart showing the process of a UE regarding RRCconnection re-establishment when a CSG cell is introduced.

FIG. 35 is a flowchart showing the process of a UE regarding RRCconnection re-establishment when a timer for permissible time beforeselecting a cell within E-UTRA is individually provided for each of acase where a whitelist is provided and a case where a whitelist is notprovided.

FIG. 36 is a flowchart showing the process of a UE regarding RRCconnection re-establishment when a timer for the case where a whitelistis provided is notified by a CSG cell.

FIG. 37 is another flowchart showing the process of a UE regarding RRCconnection re-establishment when a timer for the case where a whitelistis provided is notified by a CSG cell.

FIG. 38 is a flowchart showing the process of a UE regarding thepriority of a conventional art.

FIG. 39 is a flowchart showing the process of a UE when a priority isindividually provided for each of the case where a whitelist is providedand the case where a whitelist is not provided.

FIG. 40 is a flowchart showing the process of a UE when a priority isindividually provided for each of the case where a whitelist is providedand the case where a whitelist is not provided.

FIG. 41 is a flowchart showing the process of a UE in a cell reselectionprocedure according to a conventional art.

FIG. 42 is a flowchart showing the process of a UE, which has a CSG-IDin a whitelist, in a cell reselection procedure in which the UE uses acycle of performing measurement for cell reselection even in a casewhere a serving cell is in a good state.

FIG. 43 is a flowchart showing the process of a UE, which has a CSG-IDin a whitelist, in a cell reselection procedure in which the UE uses acycle of performing measurement for cell reselection and an offset valueeven in a case where a serving cell is in a good state.

FIG. 44 is a flowchart showing the process of a UE, which has a CSG-IDin a whitelist, in a cell reselection procedure in which the UE cancelsa cycle of performing measurement for cell reselection even in a casewhere a serving cell is in a good state and a cycle for performingmeasurement in a case where cell reselection has not been performed.

FIG. 45 is a flowchart showing the process of a UE, which has a CSG-IDin a whitelist, in a cell reselection procedure in which the UE uses ameasurement reference for starting cell reselection for a UE which has aCSG-ID in a whitelist.

FIG. 46 is a flowchart showing the process of a UE in a case where areselection procedure for a hybrid cell is varied by individuallyproviding an offset for a UE having a CSG-ID in a whitelist and for a UEhaving no CSG-ID in a whitelist.

FIG. 47 is a flowchart showing a cell reselection procedure process of aUE in a case where the method of individually providing an offset iscombined with a fifteenth embodiment.

FIG. 48 is a flowchart showing a cell reselection procedure process of aUE in a case where an offset for making cell reselection from a hybridcell difficult is provided individually.

FIG. 49 is a conceptual diagram in a case where UEs of a CSG member arecaused to be located longer than UEs of a non-CSG member in a hybridcell.

FIG. 50 shows an example of a procedure before PRACH initialtransmission in a hybrid cell.

FIG. 51 schematically shows a procedure before PRACH initialtransmission in a hybrid cell in a case where a difference of cellreselection thresholds is used.

DESCRIPTION OF REFERENCE NUMERALS

101 user equipment, 102 base station, 103 mobility management entity(MME), 104 serving gateway (S-GW)

EMBODIMENTS FOR CARRYING OUT THE INVENTION First Embodiment

FIGS. 7A and 7B are block diagrams showing an overall configuration ofan LTE mobile communication system, which is currently under discussionof 3GPP. Currently, 3GPP is studying an overall system configurationincluding closed subscriber group (CSG) cells (Home-eNodeBs (Home-eNBand HeNB) of e-UTRAN, Home-NB (HNB) of UTRAN) and non-CSG cells (eNodeB(eNB) of e-UTRAN, NodeB (NB) of UTRAN, and BSS of GERAN) and, as toe-UTRAN, is proposing the configurations of (a) and (b) of FIG. 7(Non-Patent Document 1 and Non-Patent Document 3). FIG. 7A is nowdescribed. A user equipment (UE) 71 performs transmission/receptionto/from a base station 72. The base station 72 is classified into an eNB(non-CSG cell) 72-1 and Home-eNBs (CSG cells) 72-2. The eNB 72-1 isconnected to MMES 73 through the S1 interfaces, and control informationis communicated between the eNB and the MMEs. A plurality of MMES areconnected to one eNB. The Home-eNB 72-2 is connected to the MME 73through the S1 interface, and control information is communicatedbetween the Home-eNB and the MME. A plurality of Home-eNBs are connectedto one MME.

Next, FIG. 7B is described. The UE 71 performs transmission/receptionto/from the base station 72. The base station 72 is classified into theeNB (non-CSG cell) 72-1 and the Home-eNBs (CSG cells) 72-2. As in FIG.7A, the eNB 72-1 is connected to the MMES 73 through the S1 interface,and control information is communicated between the eNB and the MMES. Aplurality of MMES are connected to one eNB. While, the Home-eNBs 72-2are connected to the MMES 73 through a Home-eNB Gateway (HeNBGW) 74. TheHome-eNBs are connected to the HeNBGW through the S1 interfaces, and theHeNBGW 74 is connected to the MMES 73 through an S1 flex interface. Oneor a plurality of Home-eNBs 72-2 are connected to one HeNBGW 74, andinformation is communicated therebetween through the S1 interfaces. TheHeNBGW 74 is connected to one or a plurality of MMES 73, and informationis communicated therebetween through a S1_flex interface.

With the configuration of FIG. 7B, one HeNBGW 74 is connected to theHome-eNBs belonging to the same CSG-ID. As a result, in the case wherethe same information such as registration information is transmittedfrom the MME 73 to a plurality of Home-eNBs 72-2 belonging to the sameCSG-ID, the information is once transmitted to the HeNBGW 74 and thentransmitted to the plurality of Home-eNBs 72-2, with the result thatsignaling efficiency is enhanced more compared with the case where theinformation is directly transmitted to each of the plurality ofHome-eNBs 72-2. While, in the case where each Home-eNB 72-2 communicatesdedicated information with the MME 73, the information is merely causedto pass through the HeNBGW 74 (to be transparent) without beingprocessed, which allows communication in such a manner that the Home-eNB72-2 is directly connected to the MME 73.

FIG. 8 is a block diagram showing the configuration of the UE (equipment71 of FIG. 7A) according to the present invention. The transmissionprocess of the UE shown in FIG. 8 is described. First, a transmissiondata buffer unit 803 stores the control data from a protocol processingunit 801 and the user data from an application unit 802. The data storedin the transmission data buffer unit 803 is transmitted to an encodingunit 804 and is subjected to encoding process such as error correction.There may exist the data output from the transmission data buffer unit803 directly to a modulating unit 805 without encoding process. The dataencoded by the encoding unit 804 is modulated by the modulating unit805. The modulated data is output to a frequency converting unit 806after being converted into a baseband signal, and then is converted intoa radio transmission frequency. After that, a transmission signal istransmitted from an antenna 807 to a base station 72. A UE 71 executesthe reception process as follows. The antenna 807 receives the radiosignal from the base station 72. The received signal is converted from aradio reception frequency to a baseband signal by the frequencyconverting unit 806 and is then demodulated by a demodulating unit 808.The demodulated data is transmitted to a decoding unit 809 and issubjected to decoding process such as error correction. Among the piecesof decoded data, the control data is transmitted to the protocolprocessing unit 801, while the user data is transmitted to theapplication unit 802. A series of process of the UE is controlled by acontrol unit 810. This means that, though not shown, the control unit810 is connected to the respective units (801 to 809).

FIG. 9 is a block diagram showing the configuration of the base station(base station 72 of FIG. 7A) according to the present invention. Thetransmission process of the base station shown in FIG. 9 is described.An EPC communication unit 901 performs data transmission/receptionbetween the base station 72 and the EPCs (such as MME 73 and HeNBGW 74).A communication with another base station 902 performs datatransmission/reception to/from another base station. The EPCcommunication unit 901 and the communication with another base stationunit 902 respectively transmit/receive information to/from the protocolprocessing unit 903. The control data from the protocol processing unit903, and the user data and control data from the EPC communication unit901 and the communication with another base station unit 902 are storedin the transmission data buffer unit 904. The data stored in thetransmission data buffer unit 904 is transmitted to the encoding unit905 and is then subjected to encoding process such as error correction.There may exist the data output from the transmission data buffer unit904 directly to a modulating unit 906 without encoding process. Theencoded data is modulated by the modulating unit 906. The modulated datais output to a frequency converting unit 907 after being converted intoa baseband signal, and then is converted into a radio transmissionfrequency. After that, a transmission signal is transmitted from anantenna 908 to one or a plurality of UEs 71. While, the receptionprocess of the base station 72 is executed as follows. A radio signalfrom one or a plurality of UEs 71 is received by the antenna 908. Thereceived signal is converted from a radio reception frequency into abaseband signal by the frequency converting unit 907, and is thendemodulated by a demodulating unit 909. The demodulated data istransmitted to a decoding unit 910 and is then subjected to decodingprocess such as error correction. Among the pieces of decoded data, thecontrol data is transmitted to the protocol processing unit 903, EPCcommunication unit 901, or communication with another base station unit902, while the user data is transmitted to the EPC communication unit901 and communication with another base station unit 902. A series ofprocess by the base station 72 is controlled by a control unit 911. Thismeans that, though not shown, the control unit 911 is connected to therespective units (901 to 910).

FIG. 10 is a block diagram showing the configuration of a mobilitymanagement entity (MME) according to the present invention. A PDN GWcommunication unit 1001 performs data transmission/reception between anMME 73 and a PDN GW. A base station communication unit 1002 performsdata transmission/reception between the MME 73 and the base station 72through the S1 interface. In the case where the data received from thePDN GW is user data, the user data is transmitted from the PDN GWcommunication unit 1001 to the base station communication unit 1002through a user plane processing unit 1003 and is then transmitted to oneor a plurality of base stations 72. In the case where the data receivedfrom the base station 72 is user data, the user data is transmitted fromthe base station communication unit 1002 to the PDN GW communicationunit 1001 through the user plane processing unit 1003 and is thentransmitted to the PDN GW.

In the case where the data received from the PDN GW is control data, thecontrol data is transmitted from the PDN GW communication unit 1001 to acontrol plane control unit 1005. In the case where the data receivedfrom the base station 72 is control data, the control data istransmitted from the base station communication unit 1002 to the controlplane control unit 1005. A HeNBGW communication unit 1004 is provided inthe case where the HeNBGW 74 is provided, which performs datatransmission/reception by the interface (IF) between the MME 73 and theHeNBGW 74 according to an information type. The control data receivedfrom the HeNBGW communication unit 1004 is transmitted from the HeNBGWcommunication unit 1004 to the control plane control unit 1005. Theprocessing results of the control plane control unit 1005 aretransmitted to the PDN GW through the PDN GW communication unit 1001.The processing results of the control plane control unit 1005 aretransmitted to one or a plurality of base stations 72 by the S1interface through the base station communication unit 1002, or aretransmitted to one or a plurality of HeNBGWs 74 through the HeNBGWcommunication unit 1004.

The control plane control unit 1005 includes a NAS security unit 1005-1,an SAE bearer control unit 1005-2, an idle state mobility managing unit1005-3 and so on, and performs overall process for the control plane.The NAS security unit 1005-1 provides, for example, security of anon-access stratum (NAS) message. For example, the SAE bearer controlunit 1005-2 manages a system architecture evolution (SAE) bearer. Forexample, the idle state mobility managing unit 1005-3 performs mobilitymanagement of an idle state (LTE-IDLE state, which is merely referred toas idle as well), generation and control of paging signaling in an idlestate, addition, deletion, update and retrieval of one or a plurality ofUEs 71 being served thereby, and tracking area (TA) list management. TheMME begins a paging protocol by transmitting a paging message to thecell belonging to a tracking area (TA) in which the UE is registered.The idle state mobility managing unit 1005-3 may manage the CSG of theHome-eNBs 72-2 to be connected to the MME, CSG-IDs and a whitelist. Inthe CSG-ID management, the relationship between a UE corresponding tothe CSG-ID and the CSG cell is managed (added, deleted, updated orretrieved). For example, it may be the relationship between one or aplurality of UEs whose user access registration has been performed witha CSG-ID and the CSG cells belonging to this CSG-ID. In the whitelistmanagement, the relationship between the UE and the CSG-ID is managed(added, deleted, updated or retrieved). For example, one or a pluralityof CSG-IDs with which user registration has been performed by a UE maybe stored in the whitelist. Although other part of the MME 73 mayperform those types of CSG-related management, through execution by theidle state mobility managing unit 1005-3, the method of using a trackingarea code in place of a CSG-ID, which is currently under discussion of3GPP meeting, can be efficiently performed. A series of process by anMME 73 is controlled by a control unit 1006. This means that, though notshown, the control unit 1006 is connected to the respective units (1001to 1005).

FIG. 11 is a block diagram showing the configuration of the HeNBGWaccording to the present invention. An EPC communication unit 1101performs data transmission/reception between the HeNBGW 74 and the MME73 by the S1_flex interface. A base station communication unit 1102performs data transmission/reception between the HeNBGW 74 and theHome-eNB 72-2 by the S1 interface. A location processing unit 1103performs the process of transmitting, to a plurality of Home-eNBs, theregistration information or the like among the data transmitted from theMME 73 through the EPC communication unit 1101. The data processed bythe location processing unit 1103 is transmitted to the base stationcommunication unit 1102 and is transmitted to one or a plurality ofHome-eNBs 72-2 through the S1 interface. The data only caused to passthrough (to be transparent) without requiring the process by thelocation processing unit 1103 is passed from the EPC communication unit1101 to the base station communication unit 1102, and is transmitted toone or a plurality of Home-eNBs 72-2 through the S1 interface. A seriesof process by the HeNBGW 74 is controlled by a control unit 1104. Thismeans that, though not shown, the control unit 1104 is connected to therespective units (1101 to 1103).

Next, an example of a typical cell search method in a mobilecommunication system is described. FIG. 12 is a flowchart showing anoutline from cell search to idle state operation performed by an userequipment (UE) in the LTE communication system. When the cell search isstarted by the UE, in Step ST1201, the slot timing and frame timing aresynchronized by a primary synchronization signal (P-SS) and a secondarysynchronization signal (S-SS) transmitted from a nearby base station.Synchronization codes, which correspond to physical cell identities(PCIs) assigned per cell one by one, are assigned to the synchronizationsignals (SS) including the P-SS and S-SS. The number of PCIs iscurrently studied in 504 ways, and these 504 ways are used forsynchronization, and the PCIs of the synchronized cells are detected(identified). Next, in Step ST1202, a reference signal RS of thesynchronized cells, which is transmitted from the base station per cell,is detected and the received power is measured. The code correspondingto the PCI one by one is used for the reference signal RS, andseparation from other cell is enabled by correlation using the code. Thecode for RS of the cell is derived from the PCI identified in StepST1201, which makes it possible to detect the RS and measure the RSreceived power. Next, in Step ST1203, the cell having the best RSreception quality (for example, cell having the highest RS receivedpower; best cell) is selected from one or more cells that have beendetected up to Step ST1202. In Step ST1204, next, the PBCH of the bestcell is received, and the BCCH that is the broadcast information isobtained. A master information block (MIB) containing the cellconfiguration information is mapped on the BCCH on the PBCH. Examples ofMIB information include the down link (DL) system bandwidth,transmission antenna number and system frame number (SFN).

In Step ST1205, next, the DL-SCH of the cell is received based on thecell configuration information of the MIB, to thereby obtain a systeminformation block (SIB) 1 of the broadcast information BCCH. The SIB1contains the information regarding access to the cell, informationregarding cell selection and scheduling information of other SIB (SIBk;k is an integer equal to or larger than 2). In addition, the SIB1contains a tracking area code (TAC). Further, the SIB1 may contain aCSG-ID. In Step ST1206, next, the UE compares the TAC received in StepST1205 with the TAC that has been already possessed by the UE. In a casewhere they are identical to each other as a result of comparison, the UEenters an idle state operation in the cell. In a case where they aredifferent from each other as a result of comparison, the UE requires acore network (EPC) (including MME and the like) to change a TA throughthe cell for performing tracking area update (TAU). The core networkupdates the TA based on an identification number (such as a UE-ID) ofthe UE transmitted from the UE together with a TAU request signal. Thecore network updates the TA, and then transmits the TAU reception signalto the UE. The UE rewrites (updates) the TAC (or TAC list) of the UE.After that, the UE enters the idle state operation in the cell.

In the LTE and universal mobile telecommunication system (UMTS), theintroduction of a closed subscriber group (CSG) cell is studied. Asdescribed above, access is permitted for only one or a plurality of UEsregistered in the CSG cell. One or a plurality of UEs registered withthe CSG cell constitute one CSG. A specific identification numberreferred to as CSG-ID is added to the thus constituted CSG. Note thatone CSG may contain a plurality of CSG cells. After being registeredwith any one of the CSG cells, the UE can access the other CSG cells ofthe CSG to which the registered CSG cell belongs. Alternatively, theHome-eNB in the LTE or the Home-NB in the UMTS is used as the CSG cellin some cases. One or a plurality of CSG cells included in one CSG-IDbelong to the same TA. For this reason, one or a plurality of CSG cellsincluded in one CSG-ID broadcast the same TAC mapped on the broadcastinformation to the UEs being served thereby. The UE registered in theCSG cell has a whitelist. Specifically, the whitelist is stored in theSIM/USIM. The CSG information of the CSG cell with which the UE has beenregistered is listed in the whitelist. Specific examples of CSGinformation include CSG-ID, tracking area identity (TAI) and TAC. Anyone of the CSG-ID and TAC is adequate as long as they are associatedwith each other. Alternatively, GCI is adequate as long as the CSG-ID,TAC and global cell identity (GCI) are associated with each other. Ascan be seen from the above, the UE which does not have a whitelist(including a case where the whitelist is empty in the present invention)is not allowed to access the CSG cell but is allowed to access only thenon-CSG cell. On the other hand, the UE which has a whitelist is allowedto access the CSG cell of the CSG-ID with which registration has beenperformed as well as the non-CSG cell.

A problem arises in a case where a UE performs cell search in a locationwith a large number of CSG cells. FIG. 13 is a conceptual diagram ofcells in a case where there are a large number of CSG cells. In thefigure, 1301 denotes a non-CSG cell of eNB, and 1302 denotes a CSG cellof Home-eNB. 1303 denotes a UE. A large number of CSG cells are requiredto be installed in apartment buildings, schools, companies and the like.The CSG cell is required to be used in such a manner that the CSG cellsare installed for each room in apartment buildings, for each classroomin schools, and for each section in companies, so that only users whohave registered with the respective CSG cells are allowed to use thoseCSG cells. Further, the CSG cells are assumed to have portable size andweight, and those CSG cells are also required to be installed or removedfrequently and flexibly. Considering the above-mentioned demands, radiowaves from a large number of CSG cells are simultaneously transmitted inone location. That is, a situation in which a UE 1303 is located in aposition within the reach of the radio waves from a large number of CSGcells as shown in FIG. 13 occurs in apartment buildings, schools,companies and the like. In such a situation, there are the UEs that havea whitelist and the UEs that do not have a whitelist. A case in whichthe UE performs cell search in this situation is considered.

FIG. 14 shows an example of a flowchart of cell search of the UE locatedin a position within the reach of the radio waves from a large number ofCSG cells. The UE starts cell search, and then the operation describedas a typical case with reference to FIG. 12 is performed. In StepST1401, synchronization is achieved by a primary synchronization signalP-SS and a secondary synchronization signal S-SS, and detection(identification) of a physical cell identity (PCI) is performed. In StepST1402, an RS is detected and the RS received power is measured. In StepST1403, the best cell is selected, and in Step ST1404, the PBCH of theselected cell is received and the MIB information is obtained. In StepST1405, the DL-SCH is received and the information of SIB1 is obtained.Then, if the TAC information of the SIB1 is identical to the TAC of theUE, the UE proceeds to the idle state operation. On the contrary, in thecase where they are not identical to each other, the operation isdifferent from that described in a typical case. As described above, theUE that has a whitelist and the UE that does not have a whitelist arepresent in such a situation. In Step ST1407, whether the UE has awhitelist is determined. In a case where the UE has a whitelist, in StepST1408, whether the TAC of the SIB1 is identical to the CSG-ID (TAC) ofthe whitelist is determined. This is because, in a case where the TAC ofthe SIB1 is not identical to the CSG-ID (TAC), registration has not beenperformed, and thus the access to the cell is prohibited. In the casewhere they are identical to each other, registration has been performed,and thus the access to the cell is permitted, whereby the UE proceeds tothe idle state operation. In the case where they are different from eachother, registration has not been performed, and thus access to the cellis not allowed, whereby the UE proceeds to Step ST1409. In Step ST1409,the UE determines whether the cell is a CSG cell. In the LTE, a CSGindicator indicating whether or not the own cell is a CSG cell isincluded in the SIB1 of the broadcast information of each cell.Therefore, it is possible to perform the determination of Step ST1409using the CSG indicator included in the information of the SIB1 that hasbeen obtained in Step ST1405. In a case where the CSG indicatorindicates a CSG cell, the UE proceeds to Step ST1410. In Step ST1410,the UE stores the PCI of the cell, and performs setting such that thePCI of the cell is excluded when cell search and selection of the bestcell are performed thereafter. This is because even if the cell is a CSGcell, it is a cell of a CSG-ID (TAC) that is not listed on the whitelistof the UE. In order that the UE stores the PCI of the CSG cell thatcannot be accessed, where the UE has performed cell search and best cellselection once, the list of the PCI that cannot be accessed or the likemay be provided for writing in the list. The PCI of the CSG cell thatcannot be accessed may be set so as to be reset or erased when the timeris provided and its timer period ends and/or when registration is madewith a new CSG-ID. In a case where the cell is determined not to be aCSG cell in Step ST1409, it is a non-CSG cell, and thus the UE proceedsto the idle state operation after TAU.

On the other hand, in the case where the UE does not have a whitelist inStep ST1407, the UE proceeds to Step ST1409. In a case where the cell isnot a CSG cell as a result of the determination of Step ST1409, the UEproceeds to the idle state operation after TAU, whereas in the casewhere the cell is a CSG cell, the UE performs the process of Step ST1410in a similar manner and performs cell search and selection of the bestcell again. In a case where a CSG cell is found after performing cellsearch and selection of the best cell again, Step ST1407, Step ST1409and Step ST1410 are performed again, which results in performing cellsearch and selection of the best cell again. As described above, inparticular, a UE that does not have a whitelist performs the cell searchfor every cell and selection of the best cell even when it is obviouslynot allowed to access the CSG cell. As a result, in a case of a UElocated in a position within the reach of radio waves from a largenumber of Home-eNBs as shown in FIG. 13, it is highly likely that alarge number of CSG cells are searched and the best cell selection isperformed, resulting in a situation where the operations of Step ST1401,Step ST1402, Step ST1403, Step ST1404, Step ST1405, Step ST1406, StepST1407, Step ST1409 and Step ST1410 are repeated several times. Thisleads to a problem that a very large amount of time is required beforeentering the idle state operation, causing a long control delay as asystem. In addition, another problem arises where a UE that has no otherchoice but to repeat cell search consumes a large amount of power. Thisproblem occurs even in a case where a UE stores the PCI of a CSG cellthat cannot be accessed in Step ST1410, and then performs setting so asto exclude the PCI of that cell in the cell search and selection of thebest cell performed thereafter. This problem becomes serious assuming afuture arrangement situation of CSG cells as described above.

In order to solve the above-mentioned problems, 3GPP discusses that allphysical cell identities (PCIs) are split (referred to as PCI-split)into ones reserved for CSG cell and the others reserved for non-CSG cell(Non-Patent Document 4). By splitting all PCIs into ones reserved forCSG cell and the others reserved for non-CSG cell, the UE that does nothave a whitelist during cell search is merely required to achievesynchronization of P-SCH and S-SCH by the PCI reserved for non-CSG cellto identify the PCI, and accordingly does not need to search a CSG cell.However, a UE always has to be aware of the PCI split information beforeperforming cell search. For this reason, 3GPP proposes that the PCIsplit range is fixed, that is, that the range of PCIs to be assigned toCSG cells and the range of PCIs to be assigned to non-CSG cells aredetermined in advance. For example, it is determined in advance thatPCIs #0 to #49 are assigned to the CSG cells and PCIs #50 to #503 areassigned to the non-CSG cells, which is described in specifications.This enables a UE to recognize these values before performing cellsearch without fail, whereby it is possible for a UE that does not havea whitelist to avoid searching a CSG cell wastefully during cell search.

However, as described above, the method of preliminarily determining therange of PCIs to be assigned to the CSG cell and the range of PCIs to beassigned to the non-CSG cell does not satisfy the demand for Home-eNBdescribed above. That is, the Home-eNBs are assumed to have portablesize and weight, and those Home-eNBs are required to be installed orremoved frequently and flexibly. Considering the above-mentioned demand,the number of CSG cells varies in accordance with various situationssuch as an operator, frequency layer, installation location and time.Therefore, there occurs a problem that the preliminary determination ofPCI split information is unable to cope with the number of CSG cellsthat varies due to flexible and frequent installation or removal ofHome-eNBs.

In order to solve the above-mentioned problem, there is disclosed amethod of mapping the PCI split information on the absolutely requiredminimum broadcast information received from cell search in an idle stateoperation, to thereby broadcast the PCI split information to UEs beingserved. FIG. 15 is a sequence diagram for broadcasting the PCI splitinformation in the LTE communication system. For example, in the LTEcommunication system, examples of the absolutely required minimumbroadcast information received from cell search to idle state operationinclude the SIB1. All base stations (Home-eNBs (CSG cells) and eNBs(non-CSG cells)) map the PCI split information into the SIB1, and mapthe BCCH including the SIB1 to the DL-SCH. Then, all base stations eachtransmit the DL-SCH and broadcast the PCI split information mapped intothe SIB1 to the user equipments (UEs) being served thereby. It isassumed here that the PCI split information transmitted from all basestations is the PCI split information on a frequency layer to which theown cell belongs. Next, FIG. 16 is a flowchart of cell search of a UE inthis method. A UE starts cell search. First, it is determined in StepST1601 whether the UE has the PCI split information. For example, whenpower supply is turned on or when the UE has not obtained the PCI splitinformation yet, the UE proceeds to Step ST1602. The UE that hasproceeded to Step ST1602 performs the method described with reference tothe flowchart shown in FIG. 14, and performs the process from StepST1602 to Step ST1611. A difference from the flowchart shown in FIG. 14is that the process of receiving the PCI split information included inthe SIB1 transmitted by the DL-SCH is performed in Step ST1606. The UEthat has received the PCI split information stores this PCI splitinformation. A PCI split information list may be provided, which maystore the PCI split information together with the PLMN and frequencylayer. The PCI split information stored in the list is configured so asto be rewritten when the broadcast information is modified.

The PCI split information stored in the list may be reset or erased whenpower supply is turned on/off, when inter-frequency layer reselection isperformed, or when inter-system reselection is performed. Whenproceeding to Step ST1611, the UE that has obtained the PCI splitinformation in Step ST1606 is capable of using the PCI split informationduring the subsequent cell search and selection of the best cell in StepST1601. The UE is determined to have the PCI split information in StepST1601, and then proceeds to Step ST1612. The UE that has proceeded toStep ST1612 is determined whether to have a whitelist. In a case wherethe UE has a whitelist, the UE proceeds to Step ST1602 and performsoperations of Step ST1602 to Step ST1611 again. However, the UE thatdoes not have a whitelist proceeds to Step ST1613 and achievessynchronization of P-SS and S-SS by the PCI of a non-CSG cell to detect(identify) the PCI by the PCI split information obtained in Step ST1606of the first cell search. The UE that has identified the PCI proceeds toStep ST1614 and performs the process of Step ST1614 to Step ST1618. Thisprocess is identical to the process in typical cell search. What mattersis that because synchronization between P-SS and S-SS is achieved by thePCI of a non-CSG cell and the PCI is detected (identified), the CSG cellis not searched. This solves the problem that a UE which does not have awhitelist repeats the operations of Step ST1602 to Step ST1611 (otherthan Step ST1609) many times even though the UE is fully aware of thatit cannot access the CSG cell, which results from the method describedwith reference to the flowchart shown in FIG. 14.

Further, for example, in a case where a UE that does not have awhitelist, which has obtained the PCI split information in the firstcell search after power-on, subsequently performs cell search again, theUE has the PCI split information. As a result, the determination of StepST1601 is “Yes”, and the UE proceeds to Step ST1612. The UE that hasproceeded to Step ST1612 performs the process of Step ST1613 to StepST1618. Accordingly, the problem that the UE that does not have awhitelist repeats the operations of Step ST1602 to Step ST1611 (otherthan Step ST1609) even though the UE is fully aware of that it cannotaccess the CSG cell, which occurs by the method described with referenceto the flowchart shown in FIG. 14, is solved also in this case.

There are various types of broadcast information blocks. In a case wherethe PCI split information is mapped into the SIB other than the SIB1, itis not received in a period of time from typical cell search to idlestate operation. In order to receive the MIB and the broadcastinformation block other than SIB1 (SIBk; k is an integer equal to orlarger than 2), the scheduling information (assigned information) of theother SIB mapped on the SIB1 needs to be received, and thus a muchlonger period of time is required, which causes a delay, and also thepower consumption of a UE increases further. The PCI split informationis mapped into the absolutely required minimum broadcast information ina time period from cell search to idle state operation, whereby the UEis not required to obtain other broadcast information block, so that itis allowed to obtain the PCI split information with low powerconsumption in a short period of time. It is possible to construct anexcellent system with a little control delay as a system. For example,in the LTE communication system, examples of the absolutely requiredminimum broadcast information received in a time period from cell searchto idle state operation include the MIB and SIB1.

With the use of the method of mapping the PCI split information on theSIB1 of the broadcast information to broadcast the PCI split informationto UEs being served, which is disclosed in the present embodiment, theUE that does not have a whitelist can avoid wastefully searching CSGcells in the second cell search and the subsequent cell search. As aresult, a problem that a long control delay occurs as a system due to avery large amount of time required for cell search to entering an idlestate operation and a problem that power is consumed considerably by aUE are solved. This enables to construct a mobile communication systemcapable of satisfying a demand for future installation of a large numberof Home-eNBs and a demand for coping with a flexible change of thenumber of CSG cells, which arises from frequent and flexibleinstallation and removal of Home-eNBs.

With the use of the method of mapping, by all cells (non-CSG cells andCSG cells), the PCI split information on the absolutely required minimumbroadcast information received for cell search to idle state operationto broadcast the PCI split information to UEs being served thereby, evena UE that has a whitelist is capable of selectively searching for a CSGcell or non-CSG cell. For example, in a case where a UE that has awhitelist preferentially accesses a CSG cell, not a non-CSG cell, the UEis capable of searching a CSG cell preferentially using the PCI splitinformation obtained through the reception of the SIB1. In this case,the operations of Step ST1612 and thereafter shown in FIG. 16 may beperformed as follows. In a case where it is determined that a UE has awhitelist in Step ST1612, the UE achieves synchronization of the primarysynchronization signal P-SS and the secondary synchronization signalS-SS by the PCI of the CSG cell, and detects (identifies) the PCI. Areference signal (RS) is detected with the identified PCI and thereceived power thereof is measured. Then, the best cell is selectedthrough comparison of the received power that has been measured. ThePBCH of the selected cell is received to receive the MIB, and further,the DL-SCH is received to receive the SIB1. The UE proceeds to the idlestate operation if a tracking area code (TAC) mapped on the SIB1 isidentical to that of a UE, while in a case where they are different fromeach other, the UE compares as to whether the tracking area code TAC ofthe SIB1 is identical to the CSG-ID (TAC) within the whitelist of theUE. In a case where they are identical to each other, the UE proceeds toan idle state operation. In a case where they are different from eachother, the UE performs cell search again. Then, in a case where cellsearch is performed using the PCI of the CSG cell and there exists nocell to be selected, the UE starts the operation of performing cellsearch using the PCI of the non-CSG cell. This enables to perform CSGcell search in a preferential manner, so that cell search and cellselection for a non-CSG cell are performed when a CSG cell that can beselected is not found.

Although the description above is given of the case where a UE that hasa whitelist preferentially accesses a CSG cell, not a non-CSG cell, a UEcan preferentially access a non-CSG cell, but a CSG cell. In a casewhere it is determined that a UE has a whitelist in Step ST1612, the UEachieves synchronization of P-SS and S-SS by the PCI of a non-CSG celland detects (identifies) the PCI. The UE detects the RS with the use ofthe identified PCI and measures the RS received power. The UE comparesthe measured RS received power to select the best cell. The UE receivesthe PBCH of the selected cell to receive the MIB, and further, receivesthe DL-SCH to receive the SIB1. In a case where the TAC mapped on theSIB1 is identical to the TAC of the UE, the UE proceeds to an idle stateoperation, or proceeds to an idle state operation after TAU in a casewhere they are different from each other. Then, in a case where the UEperforms cell search using the PCI of a non-CSG cell and there exists nocell to be selected, the UE starts the operation of performing cellsearch using the PCI of a CSG cell. This enables to perform the non-CSGcell search in a preferential manner, and thus it is possible to performcell search for CSG cells and cell selection when there exists nonon-CSG cell that can be selected.

Therefore, even a UE that has a whitelist is capable of avoidingwasteful cell search when performing the second cell search and thesubsequent search. As a result, a problem that a long control delay as asystem occurs due to a very large amount of time required for a periodof time from cell search to entering an idle state operation and aproblem that a UE consumes a large amount of power can be solved and,besides, it is possible to selectively search a CSG-cell or non-CSGcell. This enables the construction of a mobile communication systemcapable of satisfying a demand for future installation of a large numberof Home-eNBs, a demand for coping with a flexible change of the numberof CSG cells, which results from frequent and flexible installation orremoval of a Home-eNB, and demands of a UE that desires to, for example,preferentially access the registered CSG cell, not a non-CSG cell and asystem desired to be accessed.

Although the method of mapping the PCI split information on the SIB1 ofthe broadcast information to broadcast the PCI split information to UEsbeing served is described above, the method of mapping the PCI splitinformation on the MIB of the broadcast information to broadcast the PCIsplit information to UEs being served may be disclosed. In such a case,FIG. 15 is applicable as a sequence diagram. All base stations (eNBs andHome-eNBs) map the PCI split information into the MIB and map the BCCHincluding the MIB on the PBCH. Then, all base stations transmit the PBCHto the user equipments (UEs) being served thereby and broadcast the PCIsplit information mapped into the MIB. It is assumed here that the PCIsplit information to be transmitted by all base stations is the PCIsplit information on a frequency layer to which the own cell belongs.The flowchart of cell search of a UE in this method may be obtained bychanging Step ST1605 and Step ST1606 of FIG. 16 as follows. The PCIsplit information is mapped into the MIB and then is broadcast from thebase station, and thus a UE receives the PCI split information in StepST1605. While, in Step ST1606, the UE does not receive the PCI splitinformation. The above-mentioned change enables cell search. With theuse of the method of mapping the PCI split information on the MIB of thebroadcast information to broadcast the PCI split information to UEsbeing served, the above-mentioned effects can be obtained in a similarmanner.

A modified example of the first embodiment is described. The firstembodiment discloses the method of mapping the PCI split informationfrom all cells (CSG cells and non-CSG cells) on the absolutely requiredminimum broadcast information received for cell search to idle stateoperation to broadcast the PCI split information to UEs being served.The first modified example discloses the method of mapping the PCI splitinformation from only the CSG cell on the absolutely required minimumbroadcast information received for cell search to idle state operationto broadcast the PCI split information to UEs being served. FIG. 17 is asequence diagram for broadcasting the PCI split information in the LTEcommunication system. In Step ST 1702, a Home-eNB maps the PCI splitinformation into the SIB1 and maps the BCCH including the SIB1 on theDL-SCH. Then, all Home-eNBs transmit the DL-SCH to user equipments (UEs)being served thereby and broadcast the PCI split information mapped intothe SIB1. It is assumed here that the PCI split information transmittedby the Home-eNB is the PCI split information on a frequency layer towhich the own cell belongs. While, in Step ST1701, the eNB does notbroadcast the PCI split information to user equipments (UEs) beingserved thereby. In this modified example, a UE is capable of obtainingthe PCI split information only in a case where the cell obtained by thecell search and best cell selection is a CSG cell. Even in this case,however, a UE that does not have a whitelist is capable of solving aproblem that operations of Step ST1602 to Step ST1611 (other than StepST1609) of FIG. 16, such as cell search and best cell selection of theCSG cell that cannot be accessed thereafter, are repeated several timesdue to the CSG cell being selected as the best cell once.

With the use of the method of mapping the PCI split information onlyfrom the Home-eNB on the SIB1 or MIB of the broadcast information tobroadcast the PCI split information to UEs under its control, theeffects described in the first embodiment are obtained and, besides, itis not required to transmit new information (PCI split information) forCSG to the broadcast information from a non-CSG cell. This does notrequire a change in the LTE system (eUTRA/eUTRAN) that does not includeexisting CSGs, which improves compatibility.

Second Embodiment

The first embodiment discloses the method of mapping, by all cells(non-CSG cells and CSG cells), the physical cell identity (PCI) splitinformation on the absolutely required minimum broadcast informationreceived in a period of time from cell search to idle state operation tobroadcast the PCI split information to UEs being served thereby. The PCIsplit information is the PCI split information of the frequency layer towhich the own cell belongs. A second embodiment discloses the method ofbroadcasting, by all base stations (eNBs and Home-eNBs), the PCI splitinformation of the other frequency layer as the broadcast information toUEs being served thereby. FIG. 18 is a sequence diagram for broadcastingthe PCI split information on the other frequency layer in the LTEcommunication system. All base stations (Home-eNBs and eNBs) cause thePCI split information on the other frequency layer different from afrequency layer to which the own cell belongs to be included in thebroadcast information. Specifically, BCCH includes the PCI splitinformation. All base stations broadcast the broadcast information touser equipments (UEs) being served thereby. Accordingly, the UEs beingserved are allowed to obtain the PCI split information on the otherfrequency layer from the broadcast information from a serving cell. Thisenables a UE to use the PCI split information on the other frequencylayer when the processes related to the other frequency layer, such ascell search, cell selection, cell reselection and handover, arerequired. The PCI split information on the other frequency layer can beused, which enables, for example, when inter-frequency layer cell searchand cell selection are performed, the use of the PCI split informationon a desired frequency layer from the first cell search and cellselection. This enables a UE that does not have a whitelist to avoidsearching from CSG cells that cannot be accessed when cell search isperformed. This solves a problem that a long control delays occurs as asystem due to a very large amount of time required for a period of timefrom the cell search for the other frequency layer to idle stateoperation and a problem that a UE consumes a large amount of power.Accordingly, it is possible to construct a mobile communication systemcapable of satisfying a demand for future installation of a large numberof Home-eNBs and a demand for coping with a flexible change of thenumber of CSG cells, which arises from frequent and flexibleinstallation or removal of Home-eNBs. The other frequency layer may beone or more. In such a case, a UE may store the PCI split informationand a priority of the frequency or the like in pair (for example, maystore those as a list).

In the second embodiment, the broadcast information, specifically, BCCH,includes the PCI split information on the other frequency layerdifferent from the frequency layer to which the own cell belongs.Specifically, the PCI split information may be added to an SIB5 that isthe broadcast information block on which the broadcast information of afrequency layer different from that of the own cell is mapped, which iscurrently under discussion of 3GPP. The base station maps the BCCHincluding the SIB5 on which the broadcast information of the frequencylayer different from that of the own cell is mapped to the DL-SCH, andtransmits the DL-SCH to user equipments (UEs) under its control. Byreception of the SIB5, the UE is capable of performing cell search andcell selection for the other frequency layer and so on with low powerconsumption in a short period of time with the use of the PCI splitinformation on the other frequency layer of the SIB5 in the case of thecell search and cell selection for the other frequency layer and so on.

Alternatively, the PCI split information on the other frequency layerdifferent from the frequency layer to which the own cell belongs may betransmitted as the dedicated information. For example, the cell mayinclude the PCI split information on the other frequency layer differentfrom the frequency layer to which the own cell belongs in the dedicatedcontrol information, specifically, DCCH, and transmit the PCI splitinformation to UEs under its control in a dedicated manner. Stillalternatively, UEs being served by one cell may transmit a requestmessage for requesting the cell to transmit the PCI split information asdedicated information in a dedicated manner. Yet still alternatively,for example, a cell may includes the PCI split information on the otherfrequency layer different from the frequency layer to which the own cellbelongs in the paging information, specifically, PCCH, to transmit thePCI split information to UEs under its control in a dedicated manner.This enables each cell to transmit the PCI split information on theother frequency layer different from the frequency layer to which theown cell belongs as required, leading to an improvement in radioresource usage efficiency.

In the first and second embodiments, the PCI split information istransmitted from the non-CSG cell or CSG cell to UEs. The PCI splitinformation may be generated by a core network and transmitted to UEsthrough a non-CSG cell or CSG cell. Also in this case, similar effectsto those described above are obtained.

While the long term evolution (LTE) communication system in which aHome-eNB or Home-eNB in which a closed subscriber group cell (CSG cell)is used, and UMTS (the universal mobile telecommunication system) aredescribed in the first and second embodiments, the present invention isalso applicable to the UMTS using a Home-NB in which a CSG is not used.The PCI may be split for the Home-NB and the other NB to serve as thePCI split information, and the PCI split information may be included inthe broadcast information from all base stations (NB and Home-NB) to bebroadcast to UEs being served thereby. Of the broadcast information, thePCI split information may be included in the broadcast information blockrequired for the cell search and cell selection to be broadcast to UEsbeing served. This prevents a UE that has not been registered with theHome-NB from wastefully performing cell search and cell selection, whichsolves a problem that a long control delay occurs as a system due to alarge amount of time required for a period of time from cell search toidle state operation and a problem that a UE consumes a very largeamount of power. Accordingly, it is possible to construct a mobilecommunication system capable of satisfying demands for coping with thecase where a large number of Home-NBs are installed in the future andthe case where the Home-NBs need to be installed or removed frequentlyand flexibly.

Third Embodiment

The first and second embodiments disclose the method oftransmitting/receiving the PCI split information for constructing amobile communication system capable of satisfying a demand for futureinstallation of a large number of closed subscriber group (CSG) cellsand a demand for coping with a flexible change of the number of CSGcells, which arises from frequent and flexible installation or removalof the CSG cells. The present embodiment describes the problem relatingto handling of a whitelist, which arises from the installation of alarge number of CSG cells and the installation or removal of the CSGcells that is frequently and flexibly performed, and discloses themethod of solving that problem.

Currently, 3GPP discusses the method of obtaining a whitelist in a casewhere a UE performs registration with a CSG cell in the LTE system(Non-Patent Document 5). 3GPP agrees to the method in which a UE isnotified a whitelist through a non-CSG cell. FIG. 19 shows a case wherea Home-eNB (CSG cell) is located within an area of an eNB (non-CSGcell). A user equipment (UE) is located within the CSG cell area. Whileone CSG cell is located within a non-CSG cell in the figure, a pluralityof CSG cells may be located. The method of obtaining a whitelist in sucha situation is described. First, the Home-eNB owner notifies the networkoperator that the user access registration of the user equipment (UE) ofthe user has been performed. After that, the network operator notifiesthe user equipment (UE) of the whitelist from the higher layers. Thewhitelist is notified through an eNB (non-CSG cell).

FIG. 20 is a sequence diagram of the method of notifying a whitelistthrough a non-CSG cell, which is under discussion of 3GPP. The figureshows a case of the LTE communication system, in which “Owner”represents the owner of a Home-eNB and “CN” represents a core network(MME, radio network controller). The core network includes, for example,an MME, etc. The user performs user access registration of a UE with theHome-eNB, and then in Step ST2001, the owner of the Home-eNB transmits,for example, an identification number of a UE (information foridentification of a UE, such as UE-ID and IMSI) to the core network fornotifying the operator of the network that the user access registrationwith the Home-eNB of the user equipment (UE) of the user has beenperformed. In Step ST2002, the network operator that has received theidentification number of the UE (such as UE-ID and IMSI) that has beentransmitted from the owner transmits an access allowance setting requestto the Home-eNB from the core network such that the UE can access theHome-eNB. In Step ST2003, the Home-eNB that has received the accessallowance setting request performs setting so as to allow access fromthe UE. In Step ST2004, next, the network operator transmits thewhitelist from the core network to the eNB of the non-CSG cell where theHome-eNB is located. In Step ST2005, the eNB that has received thewhitelist notifies the UE of the whitelist. In Step ST2006, the UE thathas been notified the whitelist stores the whitelist in the own UE.Specifically, it is proposed to store the whitelist in the SIM/USIM(which may be storage devices such as a memory and a CPU).

A UE that does not have a whitelist is unable to access the CSG cell,and is allowed to access only the non-CSG cell. On the other hand, a UEthat has a whitelist is allowed to access the CSG cell of the registeredCSG-ID as well as the non-CSG cell.

The method of obtaining a whitelist in the case where a UE performsregistration with the CSG cell, which is under discussion of 3GPP, isdescribed above. In this method, however, a UE receives the whitelistthrough an eNB (non-CSG cell). This means that a necessary condition isthat a UE is being served by the non-CSG cell. That is, there arises aproblem that a UE is unable to obtain a whitelist when it is not beingserved by the non-CSG cell.

FIG. 21 shows a case where the Home-eNB (CSG cell) with which a UE hasperformed registration is outside the non-CSG cell area. The UE is notbeing served by the non-CSG cell, and accordingly is unable tocommunicate with the non-CSG cell. Therefore, the UE cannot obtain awhitelist even if registration with the CSG cell is performed. The UEthat does not have a whitelist is not allowed to access the CSG cell,and thus is not allowed to access the registered CSG cell as well. Thisleads to a situation in which the UE that does not have a whitelistcannot perform cell search and cell selection of the CSG cell even ifthough it is being served by the CSG cell where user access registrationhas been performed. In order to solve this problem, 3GPP proposes thatthe UE located outside the area of the non-CSG cell, which has performeduser access registration with the CSG cell, starts manual search(Non-Patent Document 5). Non-Patent Document 5 describes that in a casewhere the location of a UE is outside the area of the non-CSG cell,which had performed user access registration with the CSG cell, has notobtained a whitelist yet and is located in the area of the CSG cell withwhich user access registration had been performed, upon start of manualsearch, TAU is transmitted to the core network through the CSG cell withwhich user access registration had been performed for obtaining awhitelist.

Unfortunately, a specific manual search method is not described in theproposal of 3GPP. There is no description as to how to transmit TAU tothe core network through the CSG cell. A specific method is disclosedhere, so that a whitelist is obtained from the CSG cell in a case wherea UE that does not have a whitelist performs user access registrationwith the CSG cell. FIG. 22 discloses a specific sequence diagram in thecase where a UE that does not have a whitelist starts manual search in,for example, the LTE communication system. The user performs user accessregistration with a UE in a CSG cell (here, Home-eNB), and then in StepST2201, the owner of the CSG cell transmits, for example, anidentification number of a UE (such as UE-ID and IMSI) to the corenetwork for notifying the network operator that user access registrationof the user equipment (UE) of the user with the CSG cell has beenperformed. In Step ST2202, the network operator who has received theidentification number (such as UE-ID and IMSI) of the UE transmittedfrom the owner transmits an access allowance setting request from thecore network to the CSG cell such that the UE can access the CSG cell.In Step ST2203, the CSG cell that has received the access allowancesetting request performs setting to allow access from the UE.

In Step ST2204, next, the UE that has performed user access registrationwith the CSG cell starts manual search of a CSG cell. In this manualsearch of the CSG cell, the UE that does not have a whitelist is allowedto access the CSG cell with which user access registration has beenperformed. This enables the UE being served by the CSG cell with whichuser access registration has been performed to perform cell search andcell selection for the CSG cell. The UE that has selected the CSG cellreceives a tracking area code (TAC) transmitted from the CSG cell andcompares it with the TAC in the own UE. The UE does not have awhitelist, and accordingly the TAC in the own UE is different from theTAC transmitted from the CSG cell. Conventionally, the UE is not allowedto establish the RRC connection to the CSG cell in a case where TACs aredifferent from each other as described above. Accordingly, access to theCSG cell is not enabled, whereby it is impossible to transmit the TAU tothe core network through the CSG cell. This makes it impossible toobtain the whitelist. In the method disclosed in the present embodiment,however, even in a case of different TACs, a UE is configured to requestthe RRC connection to the CSG cell with which user access registrationhas been performed, and further, request the tracking area update (TAU)when the manual search for obtaining a whitelist is started. In StepST2204, the UE that has started manual search and selected the CSG celltransmits a request for RRC connection to the CSG cell. The CSG cellthat has received the RRC connection request from the UE allows theestablishment of RRC connection because the access allowance setting forthe UE has been made in Step ST2203. In Step ST2205, the UE which hasbeen allowed to establish the RRC connection transmits a TAU request tothe CSG cell. The number (such as UE-ID and IMSI) for identifying a UEmay be transmitted together with the TAU request message. The accessallowance setting is made for the UE, and thus in ST2206, the CSG cellthat has received the TAU request transmits the TAU request to the corenetwork together with the number for identifying a UE. In Step ST2207,the core network checks whether the UE that has transmitted the TAU isthe UE registered with the CSG cell. Specifically, the core network hasa list of the identification numbers of UEs whose user access is allowedfor each TAC or each CSG-ID, such that the identification numbers of UEswhose user access registration has been performed in Step ST2201 arerewritten (or may be deleted or added). The process of Step ST2207 isperformed by, for example, the MME 73. For example, this is performed bythe idle state mobility managing unit 1005-3 of the MME 73 shown in FIG.10.

In Step ST2207, with the use of the list, it is possible for the corenetwork to determine whether the UE that has transmitted the trackingarea update (TAU) is the UE registered with the CSG cell. In StepST2208, the core network which has determined the UE that hadtransmitted the TAU in Step ST2207 as the UE registered with the CSGcell transmits a TAU accept message to the CSG cell. In Step ST2209, theCSG cell that has received the TAU accept message transmits the TAUaccept message to the UE. In Step ST2210, the core network furthertransmits a whitelist to the CSG cell, and in Step ST2211, the CSG cellthat has received the whitelist transmits it to the UE. In Step ST2212,the UE that has notified the whitelist stores the whitelist in the ownUE. Specifically, it is proposed that the whitelist is stored in theSIM/USIM. While the description is given such that the whitelist istransmitted, not the whitelist per se but the CSG information of the CSGcell with which user access registration of the UE has been performed,which is described in the whitelist, may be transmitted. Specifically,conceivable examples of CSG information include CSG-ID, TAI and TAC,etc. Any one of those will be adequate as long as the CSG-ID isassociated with the TAI or TAC.

Alternatively, a global cell identity (GCI) will be adequate as long asthe CSG-ID, TAI, or TAC is associated with the GCI. Still alternatively,not informing of a whitelist per se, but informing of a messagerequiring a UE to write, in the whitelist, the TAC or the CSG-IDinformation on the BCCH that the UE has received through a series ofprocesses including cell search and cell selection will be adequate. InStep ST2212, the UE that has been notified the whitelist in Step ST2211stores (registers) the whitelist in the own UE. In a case where theCSG-ID, not the whitelist, is notified in Step ST2211, the CSG-ID isstored in the whitelist. In a case where the TAC or CSG-ID informationon the BCCH is required to be written in the whitelist, the TAC orCSG-ID information is stored in the whitelist. The UE that has performedregistration in the whitelist in Step ST2212 is allowed to access theCSG cell, which is not limited to the case where manual search isstarted. Note that the CSG cell described here may be any CSG cell aslong as it is a CSG cell belonging to the same CSG-ID. The methoddisclosed in the present embodiment is also applicable to a case where aUE that has already obtained a whitelist makes a change (deletion oraddition) in the whitelist.

By performing the manual search method, which is performed in a casewhere a UE that does not have a whitelist performs user accessregistration with a CSG cell, as in a manner of the sequence shown inFIG. 22, a whitelist can be obtained from the CSG cell even in a casewhere the UE is not being served by a non-CSG cell. The Home-eNB manualsearch proposed by 3GPP is premised on the fact that a UE that does nothave a whitelist is being served by the CSG cell with which user accessregistration has been made and is capable of selecting the CSG cell inmanual search, as shown in FIG. 21. Therefore, when the UE is configuredso as to make requests for RRC connection which have not been enabledconventionally and tracking area update (TAU) only for the CSG cellsbelonging to the CSG-ID of the CSG cell with which user accessregistration has been performed, the UE can access the CSG cell bymanual search, which enables to obtain a whitelist.

Fourth Embodiment

In a case of future installation of a large number of CSG cells and acase of frequent and flexible installation or removal of the CSG cells,at times, the whitelist will not be obtained only by the methoddisclosed in the third embodiment. FIG. 23 shows the case where a UE isnot being served by a non-CSG cell but is being served by a large numberof CSG cells. The situation as shown in the figure will occur in thecase where a large number of CSG cells are installed in apartmentbuildings, schools or companies in the future. As the method ofoperating CSG cells, it is studied to promote the installation in aplace outside the reach of radio waves from those non-CSG cells to allowcommunication through the CSG cells.

For example, in many cases, rooms of apartment buildings are currentlylocated in places outside the reach of radio waves from the non-CSGcells. In such cases, a CSG cell is provided to each room, and a CSG isconstituted per room to be provided with a CSG-ID. For example, it isconceivable that user access registration of a UE of a resident of eachroom is performed with the CSG of each room. In such a situation, a UEis located in a place outside the reach of radio waves from a non-CSGcell but within the reach of radio waves from a large number of CSGcells as shown in FIG. 23. Further, in such a case, the radio waves fromthe CSG cell with which user access registration has been performed donot reach a UE depending on an environment where radio waves propagate,or even if it reaches the UE, the received power is smaller comparedwith the other CSG cell in many cases. In such a situation, a UE cannotselect the CSG cell with which user access registration has beenperformed.

It is described in the above-mentioned proposal by 3GPP (Non-PatentDocument 5) that in a case where a UE whose user access registration hadbeen performed with a CSG cell has not obtained a whitelist yet and islocated in the area of CSG with which user access registration had beenperformed, the UE transmits the TAU to the core network through the CSGcell with which user access registration had been performed by startingmanual search. However, there is no description regarding the case wherea UE cannot select CSG cells (including a CSG cell having the sameCSG-ID) with which user access registration has been performed as wellas the case where the TAU is rejected. Accordingly, in such a situationthat a UE is unable to select the CSG cell with which user accessregistration has been performed, there arises a problem that a whitelistcannot be obtained by the method proposed by 3GPP (Non-Patent Document5).

Further, the following problems arise not only in the case where a UEthat does not have a whitelist registers a whitelist but also in thecase where a UE that has obtained a whitelist makes a change (deletionor addition) in the whitelist. In the above-mentioned proposal by 3GPP,there is no description regarding a UE that has a whitelist. In thesituation as shown in FIG. 23, even a UE that has a whitelist selects aCSG cell (cell that is not a suitable cell) having a CSG-ID differentfrom that of the CSG cell with which user access registration of the UEhas been performed in some cases. Also in such cases, there is nodescription regarding the case where a UE cannot select CSG cells(including a CSG cell having the same CSG-ID) with which user accessregistration has been performed. Further, there arises a problem that awhitelist cannot be obtained by the method proposed by 3GPP (Non-PatentDocument 5) where no description is given of a case where the TAU isrejected. In the discussion of 3GPP, no suggestion is made about thoseproblems and solutions to those problems are not described.

In order to solve those problems, the present embodiment discloses themethod in which, in a case where a UE that has made user accessregistration (hereinafter, including change (deletion or addition)) withthe CSG cell performs manual search, RRC connection can be establishednot only with the CSG cells belonging to the CSG-ID of the CSG cell withwhich user access registration has been performed but also with theother CSG cells and the TAU can be transmitted to the core networkthrough the CSG cell, irrespective of whether or not the presence orabsence of a whitelist is absent, to thereby enable the transmission ofTAU to the core network through the selected CSG cell even when a UEselects any CSG cell.

FIG. 24 is a sequence diagram when manual search is performed in a casewhere the establishment of RRC connection is enabled not only with theCSG cells belonging to the CSG-ID of the CSG cell with which user accessregistration has been performed but also in the other CSG cell, tothereby enable the transmission of TAU to the network through the CSGcell. The figure shows the LTE communication system in which, forexample, a Home-eNB is used. Description is given of the figure. Whileit is assumed here that the UE performs user access registration in theHome-eNB(C), Step ST2401 to Step ST2403 are operations similar to thosedescribed above, and thus description thereof is omitted. In StepST2404, a UE in the situation as shown in FIG. 23 starts manual searchof the Home-eNB in the registration or change of a whitelist. In StepST2405, the UE that has started manual search performs cell search andcell selection. In a situation as shown in FIG. 23, the UE selects theCSG cell. Irrespective of whether or not the selected CSG cell is theCSG cell with which user access registration has been performed, a UE iscapable of establishing the RRC connection to the CSG cell andtransmitting TAU to the network through the CSG cell. Therefore, in StepST2406, the UE transmits an RRC connection request to a CSG cell (inthis case, Home-eNB(A)) that is not the CSG cell (in this case,Home-eNB(C)) with which user access registration has been performed andthe Home-eNB(A) that has received the request for RRC connectionestablishment transmits establishment allowance for this establishmentrequest to the UE, such that the RRC connection is established between aUE and the Home-eNB(A). In Step ST2407 and Step ST2408, next, the UEtransmits a TAU request message to the core network through the CSG cell(Home-eNB(A)) that is not the CSG cell with which user accessregistration has been performed. The UE also transmits a UEidentification number. The UE identification number may be included inthe TAU request message, may be provided together with the TAU requestmessage, or may be transmitted as another message. Further, the RRCconnection request message or TAU request message from the UE mayinclude the information indicating the manual search has been activated,so that a CSG cell that is not the CSG cell with which user accessregistration has been performed is capable of distinguishing the case inwhich the manual search has been activated from the other case. Thisenables the CSG cell that is not the CSG cell with which user accessregistration has been performed to establish the RRC connection with theUE, and transmit/receive a series of messages such as the reception ofthe TAU request message from the UE and the transmission thereof to thecore network, which are limited to the case in which the manual searchhas been activated.

The core network that has received the TAU request message checkswhether the UE belongs to the CSG-ID of the Home-eNB(A) based on the UEidentification number that has been received as well. The methoddescribed in Step ST2207, which has been disclosed with reference toFIG. 22, is applicable to this check method. The UE identificationnumber is not registered in the CSG-ID to which the Home-eNB(A) belongs,and thus in Step ST2410 and Step ST2411, the core network which hasdetermined that the Home-eNB(A) cannot be accessed transmits a TAUreject message for the TAU request to the UE through the Home-eNB(A). InStep ST2412, the UE that has received the TAU reject message releasesthe RRC connection with the Home-eNB(A). In Step ST2413, then, the UEperforms cell selection again. In this case, cell selection may beperformed after cell search is performed again. When the cell selectionis performed again after the TAU reject message is received, the bestcell may be selected again except for the Home-eNB(A) that hastransmitted the TAU reject message, or the best cell may be selectedagain including the Home-eNB(A) that has transmitted the TAU rejectmessage. Even in the case where the best cell is selected againincluding the Home-eNB(A) that has transmitted the TAU reject message,cell selection is performed after cell search is performed again,leading to a case where the other cell serves as the best cell and theother cell is selected when, for example, an environment in which radiowaves propagate changes.

The UE that has selected the Home-eNB(B) in the retried cell selectionis allowed to request the RRC connection establishment to the CSG cellwith which user access registration has not been performed and totransmit the TAU to the network through the CSG cell, and accordinglyperforms the process of the RRC connection establishment in Step ST2414and transmits the TAU request message to the core network in Step ST2415and Step ST2416. However, the UE identification number has not beenregistered in the CSG-ID to which the Home-eNB(B) belongs in Step ST2417as in Step ST2409, and thus in Step ST2418 and Step ST2419, the corenetwork which has determined that the Home-eNB(B) cannot be accessedtransmits a TAU reject message for the TAU request to the UE through theHome-eNB(B). The UE that has received the TAU reject message releasesthe RRC connection with the Home-eNB(B) in Step ST2420. In StepST2421ST2421, then, the UE performs cell selection again as in StepST2413. The UE that has selected the Home-eNB(C) in the retried cellselection is allowed to transmit an RRC connection establishment requestto the CSG cell and the TAU to the network through the CSG cellirrespective of whether or not the user access registration with the CSGcell has been performed, and accordingly performs the process of RRCconnection establishment in Step ST2422 and transmits a TAU requestmessage to the core network in Step ST2423 and Step ST2424. The UEidentification number has been registered with CSG-ID to which theHome-eNB(C) belongs, and thus in Step ST2425, the core networkdetermines that access to the Home-eNB(C) is enabled, and then transmitsa TAU accept message for the TAU request to the UE through theHome-eNB(C) in Step ST2426 and Step ST2427. In Step ST2428, the corenetwork transmits a whitelist to the Home-eNB(C). In Step ST2429, theHome-eNB(C) that has received the whitelist transmits the whitelist tothe UE. In Step ST 2430, the UE that has received the whitelist storesthe whitelist in the own UE.

The method as described above prevents the situation where, in manualsearch of a UE, a whitelist cannot be obtained even if the CSG cell withwhich user access registration has been performed is not selected in thefirst cell selection, and then, the CSG cell where user accessregistration has been performed is selected in cell selection after afew cell selections. Accordingly, the UE is capable of obtaining awhitelist from the core network through the CSG cell where user accessregistration has been performed.

As disclosed in the present embodiment, in a case where manual search isperformed in the UE, the method is provided such that the RRC connectionestablishment is enabled not only with the CSG cell belonging to theCSG-ID of the CSG cell with which user access registration has beenperformed but also with the other CSG cells and TAU transmission to thecore network through the CSG cell is enabled irrespective of thepresence or absence of a whitelist, and that TAU can be transmitted tothe core network through the selected CSG cell even if the UE selectsany CSG cell. This makes it possible to solve the problem that awhitelist cannot be obtained in the situation where a UE cannot selectthe CSG cell with which user access registration has been performed. Inaddition, it is possible to solve a problem, in a case where the UE thathas obtained a whitelist makes a change (deletion or addition) in thewhitelist, that a whitelist cannot be obtained in a situation where theUE selects a CSG cell having a CSG-ID different from that of the CSGcell with which user access registration has been performed.Accordingly, it is possible to satisfy demands for a future system inwhich a large number of CSG cells are installed and the CSG cells areinstalled or removed frequently and flexibly.

Fifth Embodiment

The method disclosed in the fourth embodiment enables to solve theproblem that a whitelist cannot be obtained in a situation where a UEcannot select the CSG cell with which user access registration has beenperformed. The present embodiment further discloses the method ofenabling effective communication even in a case where there are a largenumber of CSG cells belong to the CSG-ID with, in which user accessregistration has not been performed.

In a situation as shown in FIG. 23, in a case where there are a largernumber of CSG cells belong to the CSG-ID with which, where user accessregistration of a UE has not been performed, a situation in which a CSGcell with which user access registration of a UE has not been performedis endlessly selected arises in the cell search and cell selection aswell as the retried cell search and cell selection when a UE performsmanual search. In such a situation, a UE repeats the RRC connectionestablishment to a large number of CSG cells and a TAU request to thecore network through the CSG cell. Further, the above-mentionedsituation in which there are a large number of UEs is assumed in futuresystem operation. For example, there is a case where CSG cells areinstalled in respective classrooms of a school and students of therespective classrooms individually register or change a whitelist. Insuch a case, a larger number of UEs repeat the RRC connectionestablishment to a large number of CSG cells and a TAU request to thecore network through the CSG cell, which is expected to result in a verylarge number. Such a situation causes a problem that the radio resourceusage efficiency and signaling efficiency reduce extremely as a system.Further, there arise a problem that a long control delay occurs as asystem due to a very large amount of time required for a period of timefrom cell search to idle state operation and a problem that a UEconsumes a large amount of power.

Further, the following problems arise in a case where the whitelist of aUE is rewritten for some reason or in a case where a UE mistakenlyreceives the contents of a whitelist transmitted from the core networkin the registration or change of the whitelist. Description is given ofa case where, for example, a UE mistakenly receives the contents of awhitelist transmitted from a core network in the registration or changeof the whitelist. In a situation where there are a large number of CSGcells as shown in FIG. 23, a case where the CSG cell belonging to theCSG-ID of a mistakenly received whitelist is selected occurs. Also insuch a case, the UE repeats the RRC connection establishment to the CSGcell belonging to the CSG-ID of the mistaken whitelist and a TAU requestto the core network through the CSG cell.

In order to solve the above-mentioned problems, in addition to themethod of the fourth embodiment, the present embodiment discloses themethod in which, when a UE performs manual search, the UE establishesthe RRC connection to a CSG cell different from the CSG cell belongingto the CSG-ID of the CSG cell with which user access registration hasbeen performed, and also when the UE further transmits a TAU request tothe core network through the CSG cell, the core network transmits awhitelist through the CSG cell before transmitting a TAU reject messageto the UE through the CSG cell. FIG. 25 is a sequence diagram of amethod of transmitting a whitelist before transmitting a TAU reject. Thefigure is described. The figure shows the LTE system in which, forexample, a Home-eNB is used. Here, the UE performs user accessregistration with the Home-eNB(C), where the operations of Step ST2501to Step ST2503 are similar to those described above and thus descriptionthereof is omitted. The UE starts manual search of the CSG cell (in thiscase, Home-eNB) in Step ST2504, and then performs cell search and cellselection in Step ST2505.

In a situation as shown in FIG. 23, when there are a large number of CSGcells which belong to the CSG-ID, with which a UE has not performed useraccess registration, the UE selects the CSG cell. As disclosed in thefourth embodiment, the UE is enabled to establish the RRC connection tothe CSG cell and transmit the TAU to the network through the CSG cell,irrespective of whether or not the selected CSG cell is the CSG cellwith which user access registration has been performed. Accordingly, inStep ST2506, a UE transmits a request for RRC connection to a CSG cell(in this case, Home-eNB(A)) that is not the CSG cell (in this case,Home-eNB(C)) with which user access registration has been performed, andthe Home-eNB(A) that has received the request for RRC connectiontransmits establishment allowance for this establishment request to aUE, so that the RRC connection is established between the UE and theHome-eNB(A). In Step ST2507 and Step ST2508, next, the UE transmits aTAU request message to the core network through the CSG cell(Home-eNB(A)) that is not the CSG cell where user access registrationhas been performed. The UE transmits the UE identification number aswell. The UE identification number may be included in the TAU requestmessage, may be provided together with the TAU request message or may betransmitted as another message. Alternatively, the RRC connectionrequest message and TAU request message from the UE may include theinformation indicating the manual search has been activated such thatthe CSG cell that is not the CSG cell with which user accessregistration has been performed is capable of distinguishing the case inwhich the manual search has been activated from the other case. Thisenables the CSG cell that is not the CSG cell with which user accessregistration has been performed to transmit/receive, to/from the UE, aseries of messages such as the RRC connection establishment, thereception of a TAU request message from the UE and the transmission to acore network, which is limited to the case in which the manual searchhas been activated. The core network that has received a TAU requestmessage checks whether the UE belongs to the CSG-ID of the Home-eNB(A)based on the received UE identification number as well. The methoddescribed with reference to Step ST2207, which is disclosed in FIG. 22,is applicable to the check method. The UE identification number has notbeen registered with the CSG-ID to which the Home-eNB(A) belongs, andthus the core network determines that the Home-eNB(A) cannot beaccessed.

In the method disclosed in the fifth embodiment, in Step ST2510, thecore network transmits the whitelist of the UE to the Home-eNB(A) beforetransmitting a TAU reject also in the case where the core network hasdetermined that the Home-eNB(A) cannot be accessed by UE. In StepST2511, the Home-eNB(A) that has received the whitelist of the UEtransmits the whitelist to the UE. The UE that has received thewhitelist in Step ST2512 stores the whitelist in the own UE. In StepST2513 and ST2514, the core network that has transmitted the whitelistof the UE to the Home-eNB(A) in Step ST2510 transmits a TAU rejectmessage for the TAU request to the UE through the Home-eNB(A). In StepST2515, the UE that has received the TAU reject message releases the RRCconnection with the Home-eNB(A).

The method described above prevents the situation in which the CSG cellwith which user access registration has been performed cannot beselected endlessly in the cell selection when the UE performs manualsearch, and thus in the first cell selection, the UE is capable ofobtaining a whitelist from the core network through the CSG cell withwhich user access registration has not been performed. Further, even ina case where only the best cell selection is allowed in the cellselection, it is possible to reliably obtain a whitelist from theselected best cell with the use of this method.

As the manual search method, not only activated before cell search andcell selection but also in the cell search, the cell identificationnumbers of one or a plurality of cells suitable for cell searchselection criteria, TAC, CSG-ID or the like may be indicated by the UE,so that a desired cell among the one or the plurality of cells ismanually selected by a user of the UE to establish the RRC connectionand transmit the TAU request to the desired cell. Through manualselection of the CSG cell with which the UE has performed user accessregistration as a desired cell, the UE is not required to performtransmission/reception for RRC connection establishment to/from the CSGcell with which user access registration has not been performed andtransmission of a TAU request message to the CSG cell.

Unfortunately, it takes time for receiving the cell identificationnumber of the cell, TAC, CSG-ID or the like because the broadcastinformation such as the SIB1 has to be received from the cell as shownin Step ST1201 to Step ST1205 of FIG. 12. In a situation where a largenumber of CSG cells are installed, it is conceivable that a very largenumber of cells are suitable for cell search selection criteria in cellsearch. Accordingly, a very large amount of time is required forreceiving the broadcast information of the all cells and indicating thecell identification number, TAC, CSG-ID or the like in the UE. Further,in a case where a UE searches for the CSG cell suitable for cell searchselection criteria, for example, the resolution for distinguishing theCSG is required and to store the broadcast information of the CSG cellin the UE is required. In a situation in which a large number of CSGcells are installed, it is conceivable that a very large number of cellsare suitable for cell search selection criteria in cell search.Therefore, the receiver of the UE becomes intricate for storing theresolution for receiving the all cells and the broadcast informationreceived from the all cells, which necessitates that a storageprocessing unit having a large amount of memory capacity to be providedin the UE. This increases the size and manufacturing cost of a UE. Inorder to avoid such a problem, the method of setting a limit on thesearch time or setting a limit on the number of cells to be searched isused in the cell search process. This is the method of selecting thebest cell within a limited time period or from a certain limited numberof cells.

In the case of using such a method, with the method in which the cellidentification numbers of one or a plurality of cells suitable for cellsearch selection criteria in cell search, TAC, CSG-ID or the like areindicated by a UE in cell search and the CSG cell with which a UE hasperformed user access registration is selected manually from the one orthe plurality of cells, there arise problems that the CSG cell will notbe searched within the search limit time, and that a limit is set oncells to be searched and the CSG cell will be outside the limit. In sucha case, there arises a problem that a UE cannot select the CSG cellwhere a UE has performed user access registration no matter how muchmanual search is performed, and a whitelist cannot be obtained.

Also in such a case, it is possible to solve the above-mentionedproblems through application of the present embodiment. In a case wherea UE that has performed user access registration (hereinafter, includingchange (deletion or addition)) with the CSG cell performs manual search,it is possible to establish the RRC connection not only to the CSG cellbelonging to the CSG-ID with which user access registration has beenperformed, but also in the other CSG cell and to perform TAUtransmission to the core network through the CSG cell, irrespective ofthe presence or absence of a whitelist, which enables transmission ofTAU to the core network through the selected CSG cell even when the UEselects any CSG cell. As a result, even in a case where the CSG cellcannot be searched within the search limit time in cell search or alimit is set on the cell to be searched and the CSG cell is outside thelimit, through selection of other CSG cell, the RRC connectionestablishment is enabled to the other CSG cell and the TAU can betransmitted to the core network through the CSG cell. This enables thecore network to transmit a whitelist through the CSG cell beforetransmitting a TAU reject message to the UE through the CSG cell,whereby the UE is capable of obtaining the whitelist.

In a case where there are a very large number of CSG cells belonging tothe CSG-ID with which UE has not performed user access registration, ina case where there are a large number of UEs in such a situation, in acase where the whitelist of the UE is rewritten for some reason, or in acase where the UE mistakenly receives the contents of the whitelisttransmitted from the core network in the registration or change of thewhitelist, the method disclosed in the present embodiment is capable ofsolving the problem that the UE wastefully repeats the RRC connectionestablishment to a large number of CSG cells and a TAU request to thecore network through the CSG cell, which result from a situation inwhich a CSG cell is endlessly selected in performing manual search inthe UE. As a result of those problems being solved, radio resource usageefficiency and signaling efficiency are prevented from reducingextremely in future system operation. Further, a period of time requiredfor the cell search to entering the idle state operation can beshortened, which solves a problem that a long control delay occurs as asystem. Moreover, a situation in which the CSG cell is selectedendlessly can be solved in performing manual search in the UE, leadingto a reduction in power consumption of the UE.

Hereinafter, a modified example of the fifth embodiment described aboveis described. The fifth embodiment discloses the method in which, when aUE performs manual search in addition to the method of the fourthembodiment, the UE establishes the RRC connection to the CSG celldifferent from the CSG cell belonging to the CSG-ID with which useraccess registration has been performed, and further, when a TAU requestis transmitted to the core network through the CSG cell, the corenetwork transmits a whitelist through the CSG cell before transmitting aTAU reject message to the UE through the CSG cell. The modified examplediscloses the method in which, when the core network transmits a TAUreject message to the UE through the CSG cell, the core network maps awhitelist on the TAU reject message and transmits the whitelist.

FIG. 26 is a sequence diagram of the method disclosed in the firstmodified example. This method is substantially identical to the methoddescribed with reference to FIG. 25 of the fifth embodiment, and thusonly differences are described here. In Step ST2609, the core networkthat has checked whether the UE belongs to the CSG-ID of the Home-eNB(A)based on the received UE identification number determines that the UEcannot access the Home-eNB(A). In Step ST2610, the core networktransmits a TAU reject message including a request for whitelistnotification to the Home-eNB(A). In Step ST2611, the Home-eNB(A) thathas received this message transmits the TAU reject message including thenotification of the whitelist to the UE. In Step ST2612, the UE that hasreceived the TAU reject message including the notification of thewhitelist in Step ST2611 stores the whitelist in the own UE. In StepST2613, the RRC connection between the UE and the Home-eNB(A) isreleased. This method enables a reduction in signaling for whitelisttransmission performed before the core network transmits the TAU rejectmessage to the UE through the CSG cell. Moreover, a TAU reject messageis transmitted/received in response to the TAU request message, and thusan effect that the compatibility with the conventional TAU request andreject method is improved is obtained.

Sixth Embodiment

In order to solve the problems described in the fifth embodiment, thepresent embodiment discloses the method in which, when the UE receives aTAU reject message n consecutive times (n is an integer equal to orlarger than 1), the UE prohibits the RRC connection establishment to thecell and the transmission of a TAU request message.

FIG. 27 is a sequence diagram of the method of prohibiting a UE fromestablishing the RRC connection to the cell when a TAU reject message isreceived from the same cell. The figure is described. The figure shows,for example, the case of an LTE system in which the Home-eNB is used. Inthis case, a UE is to perform user access registration in theHome-eNB(B), where operations of Step ST2701 to Step ST2703 are similarto those described above and thus description thereof is omitted. InStep ST2705, the UE that has started manual search of the CSG cell(here, Home-eNB) in Step ST2704 performs cell search and cell selection.In a situation as shown in FIG. 23, when there are a large number of CSGcells belonging to the CSG-ID with which the UE has not performed useraccess registration, the UE selects the CSG cell belonging to the CSG-IDwith which user access registration has not been performed, in manycases. Irrespective of whether or not the selected CSG cell is the CSGcell where user access registration has been performed as disclosed inthe fourth embodiment, the UE is allowed to establish the RRC connectionto the CSG cell, and the TAU transmission to the network through the CSGcell is enabled. Accordingly, in Step ST2706, the UE transmits the RRCconnection request to the CSG cell (in this case, Home-eNB(A)) that isnot the CSG cell (in this case, Home-eNB(B)) with which user accessregistration has been performed, and the Home-eNB(A) that has receivedthe request for RRC connection establishment transmits the establishmentallowance for this establishment request to the UE, to thereby establishthe RRC connection between the UE and Home-eNB(A).

In Step ST2707 and Step ST2708, next, the UE transmits a TAU requestmessage to the core network through the Home-eNB(A). In this case, theUE transmits the UE identification number as well. The UE identificationnumber may be included in the TAU request message, may be providedtogether with the TAU request message, or may be transmitted as anothermessage. In Step ST2709, the core network that has received the TAUrequest message checks whether the UE belongs to the CSG-ID of theHome-eNB(A) based on the received UE identification number as well. Themethod described in Step ST2207 disclosed with reference to FIG. 22 isapplicable to this check method. The UE identification number is notregistered in the CSG-ID to which the Home-eNB(A) belongs, andaccordingly the core network determines that the UE cannot access theHome-eNB(A). In Step ST2710 and Step ST2711, the core network transmitsa TAU reject message to the UE through the Home-eNB(A). In Step ST2712,the UE that has received the TAU reject message releases the RRCconnection with the Home-eNB(A). In Step ST2713 where the TAU rejectmessage has been received, the UE performs the process of prohibitingthe RRC connection establishment to the Home-eNB(A). Specifically, forexample, an RRC-connection-establishment-prohibited cell list isprovided in the UE, and the UE stores the cell identification numbers(such as PCI, cell-ID and GCI) of the Home-eNB(A) in the list. Then, theUE checks the list before establishing the subsequent RRC connection, todetermine whether the cell is one stored in the list. In the case of thecell stored in the list, the establishment of RRC connection isprohibited. On this occasion, the CSG-ID or TAC may be included in thelist, and further, the CSG-ID and TAC may be associated with the cellidentification number and stored. As a result, in a case where theHome-eNB(A) is selected again through cell search and cell selection inthe future, the UE can avoid the RRC connection establishment to theHome-eNB(A). In Step ST2714, the UE that has not obtained a whitelistuntil reaching Step ST2713 performs new cell search and cell selection.

In a case where the Home-eNB(A) is selected again, cell selection isperformed from the cells excluding the Home-eNB(A) because the RRCconnection establishment is prohibited. In Step ST2715, the UE that hasselected the Home-eNB(B) through cell selection performs the process ofestablishing the RRC connection with the Home-eNB(B). After the processof establishing the RRC connection is performed, in Step ST2716 and StepST2717, the UE transmits a TAU request message to the core networkthrough the Home-eNB(B). In Step ST2718, the core network that hasreceived the TAU request message checks whether the UE belongs to theCSG-ID (TAC) of the Home-eNB(B) based on the UE identification numberreceived together. The method described in Step ST2207 disclosed withreference to FIG. 22 is also applicable to this check method. The UEidentification number is registered with the CSG-ID to which theHome-eNB(B) belongs, and accordingly the core network determines thatthe UE can access the Home-eNB(B). In Step ST2719 and Step ST2720, thecore network transmits a TAU accept message to the UE through theHome-eNB(B). In Step ST2721 and Step ST2722, further, the core networktransmits the whitelist to the UE through the Home-eNB(B). In StepST2723, the UE that has been notified the whitelist may store thewhitelist in the own UE.

While the process of prohibiting the RRC connection establishment to thecell of which a TAU reject message has been received by a UE isdescribed in the example of the present embodiment, a UE may prohibitthe RRC connection establishment to all cells belonging to the CSG-ID ofthe cell of which a TAU reject message has been received by a UE.Alternatively, while the description is given of the process ofprohibiting the RRC connection establishment, the process of prohibitingthe transmission of a TAU request message or the process of prohibitingthe both above may be provided. Still alternatively, while thedescription is given of the process of prohibiting, by a UE, the RRCconnection establishment to the cell of which a TAU reject message hasbeen received once, the RRC connection establishment may be prohibitedin a case where TAU reject messages are received multiple consecutivetimes from the same cell. The number of times the TAU reject messagesare consecutively received from the same cell may be transmitted as thebroadcast information from the cell or may be determined in advance.

In a case where there are a very large number of CSG cells belonging tothe CSG-ID with which a UE has not performed user access registration,in a case where there are a large number of UEs in such a situation, ina case where the whitelist of the UE is rewritten for some reason, or ina case where the UE mistakenly receives the contents of the whitelisttransmitted from the core network in the registration or change of thewhitelist, the method disclosed in the present embodiment is capable ofsolving the problem that the UE wastefully repeats the RRC connectionestablishment to a large number of CSG cells and a TAU request to thecore network through the CSG cell, which results from a situation inwhich the CSG cell is endlessly selected in performing manual search inthe UE. As a result of those problems being solved, radio resource usageefficiency and signaling efficiency are prevented from reducingextremely in future system operation. Further, a period of time requiredfor the cell search to entering the idle state operation can beshortened, which solves a problem that a long control delay occurs as asystem. Moreover, a situation in which the CSG cell is selectedendlessly can be solved in performing manual search in the UE, leadingto a reduction in power consumption of the UE.

Next, a first modified example of the sixth embodiment described aboveis described. The first modified example discloses the method of mappingthe information regarding the prohibition of RRC connectionestablishment and the prohibition of TAU request message transmission onthe TAU reject message and transmitting the information to a UE by thecore network.

Description is given with reference to FIG. 27. A part of FIG. 27 may bechanged as follows. The same operations as those of the sixth embodimentare not described. In Step ST2709, the core network that has received aTAU request message checks whether the UE belongs to the CSG-ID of theHome-eNB(A) based on the received UE identification number as well. TheUE identification number has not been registered with the CSG-ID towhich the Home-eNB(A) belongs, and thus the core network determines thatthe UE cannot access the Home-eNB(A). In Step ST2710 and Step ST2711,the core network transmits a TAU reject message to the UE through theHome-eNB(A). In this case, the core network maps the informationregarding the prohibition of RRC connection establishment to theHome-eNB(A) and the prohibition of TAU request message transmission onthe TAU reject message. Specifically, a one-bit indicator may beprovided so that “1” is set in the case of prohibition and “0” is set inthe case of permission (needless to say, which may be opposite). In StepST2712, the UE that has received this releases the RRC connection withthe Home-eNB(A) and, in Step ST2713, performs the process of prohibitingthe RRC connection establishment to the Home-eNB(A).

This enables to obtain the same effects as those of the sixthembodiment. Further, this enables the core network to determine whetherthe RRC connection establishment is prohibited or the TAU requestmessage transmission is prohibited. As a result, it is possible for thecore network to cause the UE to appropriately perform the prohibitionprocess in accordance with the situation at that time, such as thesignaling load and arrangement of CSG cells, which produces the effectsuch as flexible operation as a system.

Next, a second modified example of the sixth embodiment described aboveis described. The sixth embodiment and the first modified examplethereof disclose the method of prohibiting, in a case where a UEreceives a TAU reject message, the RRC connection establishment and thetransmission of a TAU request message to the cell by the UE. However, ina prohibited situation as described above, a problem may arise in a casewhere a UE performs new user access registration (update) in a CSG cell.

In a case where a UE is prohibited from establishing the RRC connectionand transmitting a TAU request message to the CSG-ID of the CSG cellbefore new user access registration, it is conceivable that even if theUE performs new user access registration with the CSG cell, the RRCconnection establishment and transmission of a TAU request message tothe CSG cell will be prohibited continuously, whereby the CSG cellcannot be accessed. In order to solve the above-mentioned problems, thesecond modified example discloses the provision of a timer for releasingthe prohibition of RRC connection establishment and the prohibition ofTAU request message transmission. The value of the timer may bedetermined in advance as a value common to all cells or may be broadcastby the broadcast information of the CSG cell.

In the case where a value is broadcast by the broadcast information ofthe CSG cell, the value may differ from cell to cell. This enablesflexible operation for each cell. Alternatively, a value may betransmitted by being included in the TAU reject message shown in StepST2710 and Step ST2711 of FIG. 27. The value may be included in thefirst TAU reject message or a TAU reject message immediately before theRRC connection establishment is prohibited and the transmission of a TAUrequest message is prohibited. In this case, it is possible for a corenetwork to set the value of a timer, and further, a value may be set ona UE dedicatedly. This enables to appropriately set the timer value inaccordance with the situation of a system such as a signaling load orthe situation specific to a UE such as the remaining battery capacity ofa UE. The timer may be started, for example, upon the transmission ofthe TAU request message to a CSG cell. The timer may be ended when thetimer period ends, when a TAU accept message is received from the CSGcell, or when user access registration (update) is performed with a newCSG cell. FIG. 28 discloses an example of the process in a UE in a casewhere a timer is provided.

In Step ST2801, the UE that has started manual search of the Home-eNB(CSG cell) performs cell search and cell selection. In Step ST2802, theUE determines whether a timer operates because TAU is prohibited withthe CSG-ID (TAC) of the cell-selected Home-eNB. Specifically, forexample, a CSG-ID (TAC) and the timer set for the CSG-ID (TAC) may beput on the prohibition list described in the process of Step ST2713 ofFIG. 27. Determination may be made by checking the timer of the list. Ina case where the timer operates, TAU is prohibited for the cell-selectedCSG cell, and accordingly in Step ST2803, the UE performs the cellsearch and cell selection for a cell that does not belong to the CSG-ID(TAC) for which TAU is prohibited. Then, the UE proceeds to Step ST2804.On the other hand, in a case where a CSG cell for which the timer doesnot operate is selected in Step ST2802, TAU is not prohibited for theCSG cell, and accordingly the UE proceeds to Step ST2804 to transmit aTAU request to the cell-selected Home-eNB. In Step ST2805, a timer isset for the CSG-ID (TAC) of the Home-eNB to which the TAU has beenrequested, upon the transmission of a TAU request. In Step ST2806, a NASmessage for the TAU request message is received from the Home-eNB.

In Step ST2807, the UE determines whether the NAS message received inStep ST2806 is TAU reject or TAU accept. In the case of TAU accept, theUE proceeds to Step ST2808, and ends and resets the timer. In StepST2809, then, the UE registers the whitelist, and proceeds to a normalprocess. On the other hand, in the case where TAU reject is determinedin Step ST2807, the UE proceeds to Step ST2810 to again determinewhether the timer period has expired. When the timer period has expiredin Step ST2810, the UE proceeds to Step ST2812 to allow TAU for theCSG-ID (TAC) of the Home-eNB to which the TAU has been requested, andresets the timer in Step ST2813 and then performs cell search and cellselection again. In the case where the timer period has not expired inStep ST2810, the UE proceeds to Step ST2811 to perform the cell searchand cell selection again while prohibiting TAU for the CSG-ID (TAC) ofthe Home-eNB to which the TAU has been requested. Note that whether thetimer period has expired may be determined not only in the time shown inFIG. 28 but also in, for example, the process of Step ST2802. In a casewhere the timer period has expired, the UE may proceed to Step ST2804after performing the process of Step ST2812 and Step ST2813. In a casewhere the timer period has not expired, the UE may proceed to StepST2803 after performing the process of Step ST2811.

As described above, the same effects as those described in the sixthembodiment and first modified example described above are obtained byproviding the timer for releasing the prohibition of RRC connectionestablishment and the prohibition of TAU request message transmission.In addition, it is possible to solve a problem that access cannot bemade in a case where, for example, the UE performs new user accessregistration (update) to the CSG cell. This enables the construction ofmore stable system.

The LTE and UMTS in which the Home-eNB or the Home-NB in which the CSGis used are described in the sixth embodiment above. However, thepresent invention is also applicable to the UMTS using the Home-NB inwhich the CSG is not used. In the case of the UMTS using the Home-NBwhere CSG is not used, the UE accesses a Home-eNB with which user accessregistration has been performed, and when the access is successfullymade, the UE obtains the cell identification number (such as cellidentity, PCI and GCI) of the Home-NB from the Home-NB, and registers itin the whitelist (referred to as the cell identification numberwhitelist in the case of the UMTS) of the UE. Also in this case, whenthe Home-NB, which is different from the Home-NB where the UE hasperformed user access registration in the cell search and cellselection, is continuously selected, at times, the UE cannot receive thecell identification number where user access registration has beenperformed or a long period of time is required for reception.

In order to solve the above-mentioned problems, the method of the sixthembodiment is applicable to the UMTS using the Home-NB in which the CSGis not used. With the use of the method in which a UE receives a TAUreject message and the UE prohibits the RRC connection establishment tothe cell and prohibits the transmission of a TAU request message, aHome-NB different from the Home-NB from which the UE has received theTAU reject message is selected in the cell search and cell searchthereafter. This prevents a Home-NB different from the Home-NB withwhich a UE has performed user access registration from beingcontinuously selected.

Note that in a case of the UMTS communication system, it suffices thatan RNC is provided between a base station (Home-NB, NB) and a corenetwork, so that RRC messages such as an RRC connection request aretransmitted/received to/from a UE and the RNC, and that NAS messagessuch as a TAU request are transmitted/received between a UE and a corenetwork through the base station (Home-NB, NB) and RNC. This enables theapplication also to the UMTS communication system in which the Home-NBis used as the CSG cell. Therefore, a UE is prevented from wastefullyperforming cell search and cell selection, whereby it is possible tosolve a problem that a long control delay occurs as a system due to avery large amount of time required for the cell search to entering theidle state operation and a problem that a UE consumes a large amount ofpower. It is possible to construct a mobile communication system capableof satisfying demands for coping with the case where a large number ofHome-NBs are installed in the future and the case where the Home-NBs arefrequently and flexibly installed or removed.

Seventh Embodiment

The present embodiment discloses, in order to solve the problemsdescribed in the fifth embodiment, the method in which, when a corenetwork consecutively transmits a TAU reject message n-th times (n is aninteger equal to or larger than 1) to the same UE, the core networktransmits a whitelist before transmitting the n-th TAU reject message.

FIG. 29 is a sequence diagram of the method of transmitting, by a corenetwork, a whitelist before transmitting an n-th TAU reject message in acase of consecutively transmitting the TAU reject message to the same UEtwo times. The figure is described. The figure shows an LTE system inwhich, for example, Home-eNBs are used. While it is assumed here that aUE performs user access registration with the Home-eNB(B), theoperations of Step ST2901 to Step ST2903 are similar to those describedabove, and thus description thereof is omitted. The UE that has startedmanual search of a CSG cell (in this case, Home-eNB) in Step ST2904performs cell search and cell selection in Step ST2905. In a situationas shown in FIG. 23, in a case where there are a very large number ofCSG cells belonging to a CSG-ID with which the UE has not performed useraccess registration, the UE selects the CSG cell belonging to the CSG-IDwith which user access registration has not been performed in manycases. As disclosed in the fourth embodiment, the UE is allowed toestablish the RRC connection to the CSG cell and transmit TAU to thenetwork through the CSG cell, irrespective of whether or not theselected CSG cell is the CSG cell with which user access registrationhas been performed. As a result, in Step ST2906, the UE transmits arequest message for RRC connection to the CSG cell (in this case,Home-eNB(A)) that is not the CSG cell (in this case, Home-eNB(C)) withwhich user access registration has been performed, and the Home-eNB(A)that has received the request message for RRC connection transmitsallowance to this request, whereby RRC connection is established betweenthe UE and the Home-eNB(A).

In Step ST2907 and Step ST2908, next, the UE transmits a TAU requestmessage to the core network through the Home-eNB(A). On this occasion,the UE transmits a UE identification number as well. The UEidentification number may be included in the TAU request message, may betransmitted together with the TAU request message, or may be transmittedas another message. In Step ST2909, the core network that has receivedthe TAU request message checks whether the UE belongs to the CSG-ID ofthe Home-eNB(A) based on the received UE identification number as well.The method described with reference to Step ST2207, which is disclosedin FIG. 22, is applicable to the check method. The UE identificationnumber has not been registered in the CSG-ID to which the Home-eNB(A)belongs, and thus the core network determines that the UE cannot accessthe Home-eNB(A). The core network that has determined that the UE cannotaccess the Home-eNB(A) further counts the number of rejection for the UE(n=1). In Step ST2910 and Step ST2911, the core network transmits a TAUreject message to the UE through the Home-eNB(A). In Step ST2912, the UEthat has received the TAU reject message releases the RRC connectionwith the Home-eNB(A). In Step ST2913, the UE that has not obtained thewhitelist until reaching Step ST2912 performs new cell search and cellselection. In this case, when the Home-eNB(A) is selected again, in StepST2914, the UE establishes the RRC connection with the Home-eNB(A)again. In Step ST2915 and Step ST2916, next, the UE transmits the TAUrequest message to the core network through the Home-eNB(A). On thisoccasion, the UE transmits the UE identification number as well.

In Step ST2917, the core network that has received the TAU requestmessage checks whether the UE belongs to the CSG-ID of the Home-eNB(A)based on the received UE identification number as well. The UEidentification number has not been registered in the CSG-ID to which theHome-eNB(A) belongs as in Step ST2909, and thus the core networkdetermines that the UE cannot access the Home-eNB(A). The core networkthat has determined that the UE cannot access the Home-eNB(A) incrementsthe number of rejection for the UE by one (n=2). The number of rejectionfor the same UE is two, and thus the core network transmits aregistration message of the whitelist before transmitting the second TAUreject message. In Step ST2918 and Step ST2919, the core networktransmits the whitelist to the UE through the Home-eNB(B). In StepST2920, the UE that has been notified the whitelist stores the whitelistin the own UE. In Step ST2921 and Step ST2922, the core network that hastransmitted the whitelist of the UE to the Home-eNB(A) in Step ST2918transmits the second TAU reject message for the TAU request to the UEthrough the Home-eNB(A). In Step ST2923, the UE that has received theTAU reject message releases the RRC connection with the Home-eNB(A). Thenumber of times the TAU reject message is transmitted consecutively tothe same UE may be determined in advance, which can be determinedflexibly by the core network. Flexible determination by the core networkenables to appropriately transmit a whitelist to a UE in accordance witha situation at that time, such as the situations of a signaling load andreception quality of the UE, which produces the effect of flexibleoperation as a system.

In a case in which there are a very large number of CSG cells belongingto the CSG-ID, with which a UE has not performed user accessregistration, in a case where there are a large number of UEs in such asituation, in a case where the whitelist of the UE is rewritten for somereason, or in a case where the UE mistakenly receives the contents ofthe whitelist transmitted from the core network in the registration orchange of the whitelist, the method disclosed in the present embodimentis capable of solving the problem that the UE wastefully repeats the RRCconnection establishment to a large number of CSG cells and a TAUrequest to the core network through the CSG cell, which results from asituation in which a CSG cell is endlessly selected in performing manualsearch in the UE. As a result of those problems being solved, radioresource usage efficiency and signaling efficiency can be prevented fromreducing considerably in future system operation. Further, a period oftime required for the cell search to entering the idle state operationcan be shortened, which solves a problem that a long control delayoccurs as a system. Moreover, a situation in which the CSG cell isselected endlessly can be solved in performing manual search in the UE,leading to a reduction in power consumption of the UE.

Eighth Embodiment

The fourth to seventh embodiments described above disclose the method inwhich the UE establishes the RRC connection with the CSG cell belongingto the CSG-ID, with which user access registration has not beenperformed, and the TAU reject message to be transmitted to the UE by thecore network is used. In each of those cases, unfortunately, it isrequired to establish the RRC connection between the UE and the CSG cellbelonging to the CSG-ID, with which user access registration has notbeen performed, and further, it is required to transmit/receive a NASmessage such as a TAU request between the UE and the core network.

Therefore, there is disclosed a method of registering a whitelist notwith the use of the TAU reject message transmitted to the UE by the corenetwork, but with the use of an RRC connection reject messagecorresponding to an RRC connection request message, which is transmittedby the UE. This does not require the establishment of RRC connection andthe transmission/reception of a NAS message such as a TAU request. Forexample, there is disclosed a method of registering, in the methoddisclosed in the sixth embodiment, a whitelist with the use of an RRCconnection reject message to an RRC connection request messagetransmitted by a UE, not with the use of a TAU reject messagetransmitted to a UE by a core network. In a case where a UE receives anRRC connection reject message from the same cell n consecutive times (nis an integer equal to or larger than 1), the UE prohibits the RRCconnection request to the cell.

FIG. 30 is a sequence diagram of a method of prohibiting an RRCconnection request to the cell by a UE in a case of receiving an RRCconnection reject message from the same cell. The figure is described.The figure shows an LTE system in which, for example, a Home-eNB isused. While it is assumed here that a UE performs user accessregistration with the Home-eNB(B), the operations of Step ST3001 to StepST3003 are similar to those described above, and thus descriptionthereof is omitted. In Step ST3004 and Step ST3005, the core networktransmits, to all CSG cells (in this case, Home-eNBs), the informationof CSG-IDs (TACs) of the respective Home-eNBs and identification numbersof UEs belonging to the CSG-IDs. For example, the core network transmitsthe information of the identification numbers of UEs belonging to theCSG-ID of the Home-eNB(B) to the Home-eNB(B), and transmits theinformation of identification number of UEs belonging to the CSG-ID ofthe Home-eNB(A) to the Home-eNB(A). Specific examples of those pieces ofinformation may include a list in which the identification numbers ofUEs belonging to the CSG-IDs are described. The list corresponding tothe CSG-ID of each Home-eNB is transmitted to each Home-eNB from thecore network.

In Step ST3007, the UE that has started manual search of the Home-eNB inStep ST3006 performs cell search and cell selection. In a situation asshown in FIG. 23, when there are a very large number of CSG cellsbelonging to a CSG-ID with which the UE has not performed user accessregistration, the UE selects the CSG cell belonging to the CSG-ID wherethe user access registration has not been performed in many cases. Inthe present embodiment, the UE is configured so as to transmit a requestmessage for RRC connection to the CSG cell, irrespective of whether ornot the selected CSG cell is the CSG cell with which user accessregistration has been performed. The UE transmits the UE identificationnumber as well. The UE identification number may be included in an RRCconnection request message or may be provided together with an RRCconnection request message. Accordingly, in Step ST3008, the UEtransmits a request for RRC connection to the CSG cell (in this case,Home-eNB(A)) that is not the CSG cell (in this case, Home-eNB(B)) withwhich UE has performed user access registration. In Step ST3009, theHome-eNB(A) that has received this RRC connection request checks whetherthe UE belongs to the CSG-ID of the Home-eNB(A) based on the received UEidentification number as well. Through this check, it is determinedwhether or not the UE identification number is included in theidentification number list of UEs belonging to the CSG-ID of theHome-eNB(A), which has been transmitted from the core network in StepST3008.

The UE identification number has not been registered in the CSG-ID towhich the Home-eNB(A) belongs, and thus the Home-eNB(A) determines thatthe UE cannot access the Home-eNB(A). In Step ST3010, the Home-eNB(A)transmits an RRC connection reject message to the UE. In Step ST3011,the UE that has received the RRC connection reject message performs theprocess of prohibiting the transmission of RRC connection requestmessage to the Home-eNB(A). Specifically, for example, anRRC-connection-request-transmission-prohibited cell list is provided inthe UE, and the UE stores cell identification numbers (such as PCI,cell-ID and GCI) of the Home-eNB(A) in the list. Then, the UE checks thelist before transmitting the subsequent RRC connection request anddetermines whether a cell is the cell stored in the list. In the case ofthe cell stored in the list, the UE prohibits the transmission of RRCconnection request. In this case, what is stored in the list may be aCSG-ID or TAC of the CSG cell, and further, the CSG-ID or TAC may bestored by being associated with the CSG cell identification number. Thisprevents the UE from transmitting an RRC connection request to theHome-eNB(A) in a case where the Home-eNB(A) is selected again by cellsearch and cell selection in the future.

In Step ST3012, the UE that has been unable to obtain the whitelistuntil reaching Step ST3011 performs new cell search and cell selection.In the case where the Home-eNB(A) is selected again, the transmission ofRRC connection request is prohibited, and thus cell selection isperformed from the cells except for the Home-eNB(A). In Step ST3013, theUE that has selected the Home-eNB(B) through cell selection transmits anRRC connection request message to the Home-eNB(B). In Step ST3014, theHome-eNB(B) that has received the RRC connection request message checkswhether the UE belongs to the CSG-ID (TAC) of the Home-eNB(B) based onthe UE identification number received together therewith. Theabove-mentioned method is applicable to this check method as well. TheUE identification number has been registered in the CSG-ID to which theHome-eNB(B) belongs, and thus the Home-eNB(B) determines that the UE canaccess the own cell. The Home-eNB(B) that has determined that the UE canaccess the own cell may notify the UE of the whitelist in Step ST3015before transmitting an RRC connection accept message. In Step ST3016,the UE that has received the whitelist stores the whitelist in the ownUE. In Step ST3017, the Home-eNB(B) that has transmitted the whitelistto the UE transmits the RRC connection accept message. As a result, theRRC connection is established between the UE and the Home-eNB(B) (StepST3018). In Step ST3019 and Step ST3020, after that, the UE transmits aTAU request message to the core network through the Home-eNB(B). The UEtransmits the UE identification number as well.

In Step ST3021, the core network that has received the TAU requestmessage checks the CSG-ID (TAC) based on the received UE identificationnumber as well. In Step ST3022 and Step ST3023, the core network thathas checked that the UE belongs to the CSG-ID (TAC) of the Home-eNB(B)in Step ST3021 transmits a TAU accept to the UE through the Home-eNB(B).While the core network is configured to transmit the information of theCSG-ID (TAC) of each Home-eNB and the identification number of the UEsbelonging to the CSG-ID to all CSG cells (in this case, Home-eNBs) inStep ST3004 and Step ST3005, the information of the identificationnumber of the UE belonging to each CSG-ID may be transmitted to a HeNBGWconnected to the CSG cell belonging to the CSG-ID. The HeNBGW may beconfigured to transmit the received information of the identificationnumber of UE belonging to each CSG-ID to the CSG cell of the same CSG-IDconnected to the own HeNB. Alternatively, the process of transmitting,by the HeNBGW, the received information of the identification number ofUE belonging to each CSG-ID to the CSG cell of the same CSG-ID that isconnected to the own HeNB may be set such that the CSG cell which hasreceived the RRC connection request from the UE in ST3008 transmits themessage for requesting the information of the identification number ofthe UE belonging to the CSG-ID of the own CSG cell to the HeNBGW, andmay be performed when the HeNBGW receives the message.

While the present embodiment describes the process in which the UEprohibits the RRC connection request to the CSG cell from which it hasreceived the RRC connection reject message, the UE may prohibit the RRCconnection request to all cells belonging to the CSG-ID of the cell fromwhich it has received the RRC connection reject message. Further, thepresent embodiment describes the process in which the UE prohibits theRRC connection request to the CSG cell from which it has received theRRC connection reject message, the UE may prohibit the RRC connectionrequest in a case where it receives the RRC connection reject messagefrom the same cell multiple consecutive times. The number of times theRRC connection reject message is received consecutively from the samecell may be transmitted from the cell in the broadcast information ormay be determined in advance. Further, while a whitelist notification isperformed before the Home-eNB transmits the RRC connection accept, itmay be transmitted to a UE from the core network through the CSG cell ina NAS message after the UE receives the TAU accept in Step ST3023.

Next, there is disclosed a method of transmitting a whitelist with theuse of an RRC connection reject message to the RRC connection requestmessage transmitted by a UE, not with the use of a TAU reject messagetransmitted to the UE by the core network in the method disclosed in,for example, the fifth embodiment or the seventh embodiment. In thefifth or seventh embodiment, it is required to transmit, also from a CSGcell belonging to a CSG-ID with which a UE has not performed user accessregistration, a whitelist of the UE. For this reason, the core networktransmits, to all CSG cells, the information of all CSG-IDs (TACs) andthe identification numbers of UEs belonging to the CSG-IDs.

FIG. 31 is a sequence diagram of a method of transmitting a whitelistbefore a CSG cell belonging to a CSG-ID with which a UE has notperformed user access registration transmits an RRC connection rejectmessage. FIG. 31 shows a case of an LTE system in which, for example,Home-eNBs are used. While it is assumed here that a UE performs useraccess registration with a Home-eNB(C), operations of Step ST3101 toStep ST3103 are similar to those described above, and thus descriptionthereof is omitted. In Step ST3104, the core network transmits theinformation of all CSG-IDs (TACs) and the identification numbers of UEsbelonging to the CSG-IDs to all CSG cells (in this case, all Home-eNBs).Specific examples of the information may include a list in which theidentification numbers of UEs belonging to the CSG-IDs are described.The list corresponding to all CSG-IDs is transmitted from the corenetwork to all Home-eNBs. In Step ST3106, the UE that has started manualsearch in Step ST3105 performs cell search and cell selection. In asituation as shown in FIG. 23, when there are a very large number of CSGcells belonging to the CSG-ID, with which the UE has not performed useraccess registration, the UE selects the CSG cell belonging to theCSG-ID, with which user access registration has not been performed, inmany cases. In the present embodiment, the UE is allowed to transmit arequest message for RRC connection to the CSG cell irrespective ofwhether or not the selected CSG cell is the CSG cell with which useraccess registration has been performed. In addition, the UE transmitsthe UE identification number. The UE identification number may beincluded in the RRC connection request message or may be providedtogether with the RRC connection request message.

Accordingly, in Step ST3107, the UE transmits an RRC connection requestto the CSG cell (in this case, Home-eNB(A)) that is not the CSG cell (inthis case, Home-eNB(C)) with which user access registration has beenperformed. In Step ST3108, the Home-eNB(A) that has received this RRCconnection request checks which CSG-ID the UE belongs to, based on thereceived UE identification number as well. This check is performed withthe use of the list of the identification numbers of UEs belonging toall CSG-IDs, which has been transmitted from the core network in StepST3104. The Home-eNB(A) searches for and identifies a CSG-ID containingthe UE identification number. In Step ST3109, the Home-eNB(A) notifiesthe UE of a whitelist using the identified CSG-ID. In Step ST3110, theUE that has received the whitelist stores the whitelist in the own UE.In Step ST3111, the Home-eNB(A) that has notified the UE of thewhitelist in Step ST3109 transmits an RRC connection reject message tothe UE.

While the core network transmits the information of all CSG-IDs (TACs)and the identification numbers of UEs belonging to the CSG-IDs to allCSG cells (in this case, all Home-eNBs) in Step ST3104, the informationof the identification numbers of UEs belonging to the respective CSG-IDsmay be transmitted to all HeNBGWs. The HeNBGW may transmit theinformation of the identification numbers of UEs belonging to allCSG-IDs to all CSG cells connected to the own HeNB. Further, the processof transmitting, by all HeNBGWs, the received information of theidentification numbers of UEs belonging to all CSG-IDs to all CSG cellsconnected to the own HeNB may be set such that the CSG cell which hasreceived the RRC connection request from the UE in Step ST3107 transmitsthe message for requesting the information of the identification numbersof UEs belonging to all CSG-IDs to the HeNBGWs, and may be performed ina case where the HeNBGWs receive the message. The above-mentioned methodenables to transmit, also from a CSG cell belonging to a CSG-ID withwhich a UE has not performed user access registration, a whitelist ofthe UE.

In addition to the effects described in the fourth to seventhembodiments, the adoption of the method disclosed above does not requirethe establishment of the RRC connection and transmission/reception of aNAS message such as the TAU request. As a result, it is possible toachieve an improvement in radio resource usage efficiency, a reductionin signaling load, a reduction in control delay as a system, and areduction in power consumption of a UE.

Ninth Embodiment

In the third embodiment to the seventh embodiment described above, theUE that has performed user access registration with a CSG cell transmitsa TAU request to the core network for obtaining a whitelist from a corenetwork. The description is given that the core network that hasreceived the TAU request from the UE checks a CSG-ID (TAC) with the useof the identification number of the UE and transmits a whitelist to theUE.

The core network may be configured to transmit a whitelist in accordancewith the method described above without fail, upon transmission of a TAUrequest message from a UE. However, the TAU request message is generatednot only for obtaining a whitelist from a core network but also due toother causes. For example, in a case where a UE has obtained two CSG-IDsin a whitelist and moves from the CSG cell belonging to one CSG-ID tothe CSG cell belonging to the other CSG-ID, the whitelist is notrequired to be registered (updated) anew, but TACs of two CSG cells aredifferent from each other. Accordingly, the UE transmits the TAU requestto the core network. In such a case, though the core network is notrequired to transmit a whitelist to the UE, the whitelist is transmittedto the UE, which causes a problem that a signaling load is increasedwastefully.

Further, in the methods disclosed in the first modified example of thesixth embodiment and the seventh embodiment, the core network is capableof determining the prohibition of RRC connection establishment and TAUrequest transmission for the UE, but also in such a case, the corenetwork desirably knows whether the TAU request message transmitted bythe UE is for requesting a whitelist. If the core network does not knowthe above, the core network also takes a TAU request message transmitteddue to other causes into consideration, leading to an inefficientoperation. The present embodiment discloses, in order to solve theabove-mentioned problem, that the information indicating that themessage is a request for (registering) updating a whitelist or forrequesting transmission (notification) of a whitelist is mapped on theTAU request message.

For example, in the example shown in FIG. 25, which is described in thefifth embodiment, in Step ST2507 and Step ST2508, the UE transmits a TAUrequest to the core network through the Home-eNB(A). The informationindicating that the message is a request for (registering) updating awhitelist is mapped on the TAU request message, and the core network isnotified that the cause of the message is a request for (registering)updating a whitelist, together with the TAU request. With theabove-mentioned configuration, the core network is capable of knowingthat the UE requests the (registration) update of the whitelist. On theother hand, in a case where the information indicating that the messageis a request for updating (registering) a whitelist is not mapped on theTAU request message, the core network knows that the TAU request messageis not a request for (registering) updating a whitelist, and accordinglyis not required to transmit the whitelist to the UE. As a specificmethod of mapping the information indicating that the message is arequest for (registering) updating a whitelist on the TAU requestmessage, a whitelist (registration) update request may be added to theType information of TAU. The Type information may be expressednumerically. Alternatively, a one-bit indicator indicating whether ornot the message is a request for (registering) updating a whitelist maybe provided on the TAU request message.

The adoption of the method described above enables to prevent anincrease in signaling load due to the transmission of a whitelist to theUE, which is intrinsically unnecessary, though the core network is notrequired to transmit a whitelist to the UE. In addition, in a case wherethe core network determines whether to prohibit the establishment of RRCconnection and transmission of the TAU request for the UE, it ispossible to solve a problem that an inefficient operation occurs inconsideration of the TAU request message transmitted due to othercauses.

Next, a first modified example of the present embodiment is described.The method of mapping the information used for requesting (registration)update of a whitelist on a TAU request message is applicable to thethird embodiment to the seventh embodiment. Disclosed here is that forapplication to the method disclosed in the eighth embodiment, theinformation indicating that the message is a request for (registering)updating a whitelist or a request for transmitting (notifying) awhitelist is mapped on the RRC connection request message.

In the eighth embodiment, a whitelist is transmitted with the use of anRRC connection reject message to an RRC connection request messagetransmitted by a UE. It is described that a CSG cell that has receivedthe RRC connection request from the UE checks a CSG-ID (TAC) using anidentification number of the UE and transmits the whitelist to the UE.The CSG cell may be configured to transmit a whitelist in accordancewith the above-mentioned method without fail upon the transmission of anRRC connection request message from a UE, which causes a problem thatthe radio resource usage efficiency decreases wastefully as describedabove, further leading to an inefficient operation. The first modifiedexample discloses, in order to solve the above-mentioned problem, thatthe information indicating that the message is a request for(registering) updating a whitelist is mapped on an RRC connectionrequest message.

For example, in a case of the example shown in FIG. 31, which isdescribed in the eighth embodiment, the UE transmits an RRC connectionrequest to a Home-eNB(A) in Step ST3107. The UE maps the informationindicating that the message is a request for (registering) updating awhitelist on the RRC connection request message and notifies theHome-eNB(A) that the cause of the message is a request for (registering)updating a whitelist, together with the RRC connection request. Thisallows the Home-eNB(A) to know that the UE requests (registration)update of a whitelist. On the other hand, in a case where theinformation indicating that the message is a request for (registering)updating a whitelist is not mapped on the RRC connection requestmessage, the Home-eNB(A) knows that the RRC connection request messageis not a request for (registering) updating a whitelist, and accordinglyis not required to transmit the whitelist to the UE.

As a specific method of mapping the information indicating that themessage is a request for (registering) updating a whitelist on an RRCconnection request message, a whitelist (registration) update requestmay be added as the cause information of an RRC connection requestmessage. The cause information may be expressed numerically.Alternatively, a one-bit indicator indicating whether or not the messageis a request for (registering) updating a whitelist may be provided onthe RRC connection request message. While this modified exampledescribes the case of the application to the method disclosed in theeighth embodiment, this modified example is also applicable to the thirdembodiment to the seventh embodiment. It is possible to apply thismodified example when RRC connection is requested, which is performedwhen (registration) update of a whitelist is requested.

In addition to the effects described in the eighth embodiment, themethod disclosed in the present embodiment is further capable of solvingthe above-mentioned problem that a registration (update) notificationmessage is transmitted to the UE though a CSG cell is not required totransmit a whitelist to the UE, which wastefully reduces a radioresource. In addition, the method is capable of solving theabove-mentioned problem that, in a case where, for example, a CSG celldetermines whether to prohibit the transmission of an RRC connectionrequest to the UE, an inefficient operation occurs also in considerationof an RRC connection request message that has been transmitted due toother causes. Further, as a result of the information indicating thatthe message is a request for (registering) updating a whitelist beingmapped on a TAU request message or an RRC connection request message,the execution of the establishment of RRC connection to a CSG cell thatis not the CSG cell with which a UE has performed user accessregistration and the execution of the transmission of a TAU requestmessage to the core network through the CSG cell are not limited to thecase in which the manual search has been activated. Through applicationof the methods described in the present embodiment and its modifiedexample, it suffices that, for requesting (registering) update of awhitelist, a UE is permitted to perform the establishment of RRCconnection to a CSG cell that is not the cell with which the UE hasperformed user access registration and the transmission of a TAU requestmessage to the core network through the CSG cell. This enables, forexample, after the user access registration, to automatically performthe communication for obtaining a whitelist without starting manualsearch and to perform the communication for obtaining a whitelistperiodically (for example, periodically in a cycle determined inadvance) before obtaining a whitelist without starting manual search. Asa result, the procedure until a UE obtains a registered (updated)whitelist can be performed flexibly, and it is possible to cope with thesituation in which a large number of CSG cells are installed and useraccess registration is performed in various locations in the future. Asa result of the methods described in the present embodiment and itsmodified example being applied, it is not required to include theinformation indicating that a UE has started manual search in an RRCconnection and a TAU request as disclosed in the fourth and fifthembodiments, leading to a reduction in signaling amount.

Tenth Embodiment

In the fourth embodiment to the seventh embodiment, the UE that hasperformed user access registration with a CSG cell transmits a TAUrequest to the core network through the CSG cell for obtaining awhitelist from a core network (CN). It is described that the corenetwork that has received the TAU request from the UE checks a CSG-ID(TAC) with the use of the identification number of the UE and, in a caseof determining that it cannot access the CSG cell, transmits a TAUreject message to the UE through the CSG cell. Besides, the descriptionis given of the method of determining, by the UE, a subsequent operationin response to the TAU reject message received from the core networkthrough the CSG cell. In such a case, the UE preferably knows whetherthe TAU reject message received through the CSG cell is transmitted inresponse to the TAU request message for requesting (registration) updateof a whitelist and, otherwise, a TAU reject message transmitted due toother causes is also taken into consideration, leading to an inefficientoperation.

On the other hand, 3GPP discusses that the cause information indicating“no suitable cells” is mapped on the TAU reject message or RRCconnection reject message. As described above, however, the “suitablecell” is defined in several ways, and thus it is difficult to identifyany definition into which the cell does not fall. The present embodimentdiscloses, in order to solve the above-mentioned problem, that theinformation indicating the cause of rejection is that the UEidentification number is not registered in the CSG-ID to which the CSGcell belongs is mapped on the TAU reject message.

For example, in the case of the example shown in FIG. 27, which isdescribed in the sixth embodiment, the core network transmits a TAUrequest reject message to the UE through the Home-eNB(A) in Step ST2710and Step ST2711. The information indicating that the cause of rejectionis that the UE identification number is not registered in the CSG-ID towhich the Home-eNB(A) belongs is mapped on the TAU reject message, tothereby notify that the cause is that the UE identification number isnot registered in the CSG-ID to which the Home-eNB(A) belongs. Thisenables the UE to know that the cause of the received TAU request rejectmessage is that the UE identification number is not registered in theCSG-ID to which the CSG cell belongs. On the other hand, in a case wherethe information indicating that the cause of rejection is that the UEidentification number is not registered in the CSG-ID to which a CSGcell belongs is not mapped on a TAU reject message, it is understoodthat the TAU reject message is transmitted due to any other causes.

As a specific method of mapping, on the TAU reject message, theinformation indicating that the cause of rejection is that the UEidentification number is not registered in the CSG-ID to which the CSGcell belongs, the information indicating that the UE identificationnumber is not registered in the CSG-ID to which the CSG cell belongs maybe added to the cause information of the TAU reject message. The causeinformation may be expressed numerically. Alternatively, a one-bitindicator indicating whether or not the cause is the UE identificationnumber is not registered in the CSG-ID to which the CSG cell belongs maybe provided on the TAU request reject message.

In addition to the effects described in the fourth to seventhembodiments, the method disclosed in the present embodiment enables tosolve the above-mentioned problem that an insufficient operation iscaused also in consideration of the TAU reject message transmitted dueto other causes in the case where a UE determines whether to prohibitthe establishment of RRC connection and the transmission of TAU requestto the TAU reject message transmitted from the core network.

Next, a first modified example of the tenth embodiment described aboveis described. Disclosed here is that the information indicating that thecause of rejection is that the UE identification number is notregistered in the CSG-ID to which the CSG cell belongs is mapped on theRRC connection reject message, for application to the method disclosedin the eighth embodiment. The eighth embodiment describes that the UEperforms the process of prohibiting the transmission of an RRCconnection request message, with the use of the RRC connection rejectmessage to the RRC connection request message transmitted by the UE. TheUE may be configured to prohibit the transmission of an RRC connectionrequest message to the CSG cell without fail upon the transmission ofthe RRC connection reject message from the CSG cell. However, thiscauses an inefficient operation as described above.

The first modified example discloses, in order to solve theabove-mentioned problem, that the information indicating that the causeof rejection is that the UE identification number is not registered inthe CSG-ID to which the CSG cell belongs is mapped on an RRC connectionreject message. For example, in the case of the example shown in FIG.31, which is described in the eighth embodiment, in Step ST3110, the UEreceives RRC connection reject from the Home-eNB(A). The Home-eNB(A)maps, on the RRC connection reject message, the information indicatingthat the cause of rejection is that the UE identification number is notregistered in the CSG-ID to which the Home-eNB(A) belongs, and notifiesthe UE that the cause of rejection is that the UE identification numberis not registered in the CSG-ID to which the Home-eNB(A) belongs. Thisenables the UE to know that the received RRC connection reject messageis transmitted because the UE identification number is not registered inthe CSG-ID to which the CSG cell belongs. On the other hand, in a casewhere the information indicating that the cause of rejection is that theUE identification number is not registered in the CSG-ID to which theCSG cell belongs is not mapped on the RRC connection reject message, itis possible to know that the cause of rejection is that the UEidentification number is not registered in the CSG-ID to which the CSGcell belongs.

As a specific method of mapping the information indicating that thecause of rejection is that the UE identification number is notregistered in the CSG-ID to which the CSG cell belongs on the RRCconnection reject message, the information indicating that the UEidentification number is not registered in the CSG-ID to which the CSGcell belongs may be added to the cause information of the RRC connectionreject message. The cause information may be expressed numerically.Alternatively, a one-bit indicator indicating whether or not the causeis the UE identification number is not registered in the CSG-ID to whichthe CSG cell belongs may be provided on the RRC connection rejectmessage.

In addition to the effects described in the eighth embodiment, themethod disclosed in the present embodiment enables to solve the problemthat an insufficient operation is caused also in consideration of theRRC connection reject message transmitted due to other causes in thecase where a UE determines whether to prohibit the RRC connectionrequest when receiving an RRC connection reject message from the CSGcell.

Eleventh Embodiment

The description is given of the case where a UE mistakenly receives thecontents of a whitelist transmitted from a core network at times in theregistration or change of the whitelist. In such a case, there occurs acase where a CSG cell belonging to the CSG-ID of the mistakenly receivedwhitelist is selected in a situation where there are a large number ofCSG cells, and accordingly a UE repeats the establishment of RRCconnection to the CSG cell belonging to the CSG-ID of the mistakenlyreceived whitelist and the TAU request to the core network through theCSG cell many times. As a result, there arises a problem of extremereductions in radio resource usage efficiency and signaling efficiencyas a system. Further, a problem that a long control delay occurs due toa very large amount of time period required from cell search to enteringan idle state operation and a problem that a UE consumes a large amountof power are caused.

The present embodiment discloses, in order to solve those problems, themethod of transmitting the success/failure (Ack/Nack) of whitelistreception to a core network by a UE in an explicit manner. FIG. 32 is asequence diagram of the method of transmitting, when a whitelist isregistered, the success/failure (Ack/Nack, complete/incomplete) ofwhitelist reception by a UE to a core network in an explicit manner. Thefigure shows a case of LTE communication system using, for example, aHome-eNB. The figure is described below. While it is assumed here that aUE performs user access registration with a Home-eNB(C), operations ofStep ST3201 to Step ST3203 are similar to those described above, andthus description thereof is omitted. In Step ST3205, the UE that hasstarted manual search of a CSG cell (in this case, Home-eNB) in StepST3204 performs cell search and cell selection. In a situation as shownin FIG. 23, when there are a larger number of CSG cells belonging to theCSG-ID with which a UE has not performed user access registration, theUE selects a CSG cell. As described in the fourth embodiment, a UE isenabled to establish RRC connection to the CSG cell irrespective ofwhether the selected CSG cell is the CSG cell with which user accessregistration has been performed, and accordingly is enabled to transmitTAU to the network through the CSG cell. As a result, in Step ST3206,the UE transmits a request for RRC connection to a CSG cell (in thiscase, Home-eNB(A) that is not the CSG cell (in this case, Home-eNB(C))with which user access registration has been performed, and theHome-eNB(A)) that has received this request for RRC connection transmitsestablishment allowance to this establishment request to a UE, wherebyRRC connection is established between the UE and the Home-eNB(A).

In Step ST3207 and Step ST3208, next, the UE transmits a TAU requestmessage to the core network through the Home-eNB(A). On this occasion,the UE transmits a UE identification number as well. The UEidentification number may be included in the TAU request message, may beprovided together with the TAU request message, or may be transmitted asthe other message. The core network that has received the TAU requestmessage checks whether the UE belongs to the CSG-ID of the Home-eNB(A)based on the received UE identification number as well. The methoddescribed with reference to Step ST2207, which is disclosed in FIG. 22,is applicable to this check method. The UE identification number is notregistered in the CSG-ID to which the Home-eNB(A) belongs, andaccordingly the core network determines that the UE cannot access theHome-eNB(A). In the present embodiment, for example, the methoddisclosed in the fifth embodiment is used. Also in a case where the corenetwork determines that the UE cannot access the Home-eNB(A), in StepST3210, the core network transmits the whitelist of the UE to theHome-eNB(A) before transmitting TAU reject. In Step ST3211, theHome-eNB(A) that has received the whitelist of the UE transmits thewhitelist to the UE.

On this occasion, in Step ST3212, the UE that has received the whitelisttransmits Ack indicating the success of whitelist reception to theHome-eNB(A). This Ack may be provided as a NAS message. In Step ST3213,the Home-eNB(A) that has received Ack indicating the success ofwhitelist reception from the UE transmits Ack indicating the success ofwhitelist reception to the core network. In Step ST3215, the corenetwork that has received AcK indicating the success of whitelistreception transmits, to the Home-eNB(C) with which the UE has performeduser access registration, the information for notifying that the UE hascompleted the user access registration. On the other hand, in StepST3214, the UE stores the received whitelist in the own UE. In StepST3216 and Step ST3217, the core network that has received Ackindicating the success of whitelist reception in Step ST3213 transmits aTAU reject message for the TAU request to the UE through theHome-eNB(A). In Step ST3218, the UE that has received the TAU rejectmessage releases the RRC connection with the Home-eNB(A).

In Step ST3212, the UE that has failed to receive the whitelist in StepST3211 transmits Nack indicating the failure of whitelist reception tothe Home-eNB(A). This Nack may be provided as a NAS message. In StepST3213, the Home-eNB(A) that has received Nack indicating the failure ofwhitelist reception from the UE transmits Nack indicating the failure ofwhitelist reception to the core network. The core network that hasreceived Nack indicating the failure of whitelist reception transmitsthe whitelist to the UE through the Home-eNB(A) again in Step ST3210 andStep ST3211. The process described above is repeated until the UEsuccessfully receives the whitelist. If the UE succeeds in reception,the process of Step ST3212 and thereafter is performed. Theabove-mentioned method enables to considerably reduce the probabilitythat the UE will mistakenly receive the contents of the whitelisttransmitted from the core network. This solves a problem that, in asituation in which a large number of CSG cells are present as describedabove, a UE mistakenly selects the CSG cell belonging to the CSG-ID ofthe whitelist that has been received mistakenly and repeats theestablishment of RRC connection to the CSG cell many times and a TAUrequest to the core network through the CSG cell. By solving thoseproblems, it is possible to avoid extreme reductions in radio resourceusage efficiency and signaling efficiency in a future system operation.

While the fourth to eleventh embodiments of the present inventiondescribe the registration of a whitelist, which are also applicable notonly to the registration of a whitelist, but also to the update(including deletion and addition) of a whitelist. The examples of thefirst to eleventh embodiments of the present invention describe thecommunication system using an LTE system in which the Home-eNB is usedas a CSG cell, which are also applicable to a case of the UMTScommunication system in which the Home-NB is used as a CSG cell. In thecase of the UMTS communication system in which the Home-NB is used as aCSG cell, an RNC may be provided between a base station (Home-NB, NB)and the core network, so that an RRC message such as an RRC connectionrequest is transmitted/received between the UE and the RNC and that aNAS message such as a TAU request is transmitted/received between the UEand the core network through the base station (Home-NB, NB) and the RNC.This also allows the application to the case of the UMTS communicationsystem in which the Home-eNB is used as a CSG cell.

Twelfth Embodiment

Non-Patent Document 6 discloses the process of radio resource control(RRC) connection re-establishment as an LTE mobile communication system.FIG. 33 shows the process flow of the RRC connection re-establishment asa UE. In Step ST 3301, the UE determines whether or not radio linkfailure has been detected. As a result, in a case where radio linkfailure has been detected, the UE proceeds to Step ST3305, or proceedsto Step ST3302 in a case where it has not been detected. In Step ST3302,the UE determines whether or not handover failure has occurred. As aresult, in a case where handover failure has occurred, the UE proceedsto Step ST3305, or proceeds to Step ST3303 in a case where handoverfailure has not occurred. In Step ST3303, the UE determines whether ornot there exists an indication of integrity failure from lower layers.As a result, in a case where there is an indication of integrityfailure, the UE proceeds to Step ST3305, or proceeds to Step ST3304 in acase where there is no indication. In Step ST3304, the UE determineswhether or not RRC connection reconfiguration failure has occurred. As aresult, the UE proceeds to Step ST3305 in a case where RRC connectionreconfiguration failure has occurred, or proceeds to Step ST3301 in acase where it has not occurred. The UE that has returned to Step ST3301repeats the process of Step ST3301, Step ST3302, Step ST3303 and StepST3304. Step ST3301, Step ST3302, Step ST3303 and Step ST3304 areprocessed in an arbitrary order, and may be processed at the same time.

Description is given below of radio link failure where a UE determinesthe presence or absence of detection in Step ST3301. The time periodrequired for permitting radio link recovery after the detection of aphysical layer problem is, for example, T310. It is also possible todefine a counter value of physical layer failure from the detection of aphysical layer problem to the permission of radio link recovery, insteadof T310. Further, the time period required for permitting radio linkrecovery after the reception of random access problem indication fromthe MAC is, for example, T312.

The UE detects radio link failure in a case where the above-mentionedtimers (T310, T312) end. Note that the timers (T310, T312) are mapped toa system information block type 2 (SIB2) as part of UE-timer andconstants information element, and the base station (on a network side)notifies the UE of the timers on the PDSCH (DL-SCH) using the BCCH.

Description is given below of handover failure that is determined by aUE in Step ST3302. The UE executes handover upon reception of an RRCmessage that is a trigger of handover. In a case where the RRCconnection reconfiguration message includes mobility controlinformation, the UE sets a timer (for example, T304) included in themobility control information. In a case where the MAC completes a randomaccess procedure, the UE stops the timer (T304). The UE determines thatthe handover failure has occurred in a case where the timer (T304) hasended. That is, the timer (T304) defines the allowed time required forthe UE executing handover to the MAC completing a random accessprocedure. Note that the timer (T304) is mapped to the RRC connectionreconfiguration message as part of the mobility control informationelement and the base station (on a network side) notifies the UE of thetimer as the non access stratum (NAS) dedicated information.

Description is given below of the RRC connection reconfiguration failurethat is determined by a UE in Step ST3304. In a case where the RRCconnection reconfiguration message includes the configuration with whichthe UE is unable to comply, the UE determines that the RRC connectionreconfiguration failure has occurred. Note that the base station (on anetwork side) notifies the UE of the RRC connection reconfigurationmessage as the NAS dedicated information. In Step ST3305, the UE stopsthe timer of the time (T310) for permitting radio link recovery afterdetecting a physical layer problem, and then proceeds to Step ST3306. InStep ST3306, the UE stops the timer of the time (T312) for permittingradio link recovery after receiving a random access problem indicationfrom the MAC, and then proceeds to Step ST3307. In Step ST3307, the UEstarts the timer (for example, T311) of the allowed time for thedetection of radio link failure, determination of handover failure,determination of integrity failure or determination of RRC connectionreconfiguration failure to the selection of a cell in the E-UTRA, andthen proceeds to Step ST3308. Note that the timer (T311) is mapped tothe system information block type (SIB2) as part of UE-timer andconstants information element, and the base station (on a network side)notifies the UE of the timer on the PDSCH using the BCCH. In StepST3308, the UE resets media access control (MAC) and then proceeds toStep ST3309. In Step ST3309, the UE reconfigures the radio link control(RLC) of all radio bearers (RBs) that have been set, and then proceedsto Step ST3310.

In Step ST3310, the UE determines whether the T311 timer has ended.

As a result, the UE proceeds to Step ST3311 in a case where the timerhas ended (the timer has timed out, completed or expired), or proceedsto Step ST3314 in a case where the timer has not ended.

In Step ST3311, the UE resets the reconfiguration of the MAC and the RLCof all radio bearers that have been set, and then proceeds to StepST3312.

In Step ST3312, the UE releases all radio resources, and then proceedsto Step ST3313. In Step ST3313, the UE changes to the RRC-IDLE state.

In Step ST3314, the UE determines whether or not the E-UTRA cell hasbeen selected in accordance with a cell selection process, or a cellreselection process. As a result, the UE proceeds to Step ST3315 in acase where the E-UTRA cell has been selected, or proceeds to Step ST3317in a case where the E-UTRA cell has not been selected. In Step ST3315,the UE stops the timer T311 and then proceeds to Step ST3316. In StepST3316, the UE transmits an RRC connection reestablishment requestmessage to the network side.

In Step ST3317, the UE determines whether or not an inter-radio accesstechnology (RAT) cell has been selected in accordance with the cellselection process. As a result, the UE proceeds to Step ST3311 in a casewhere the inter-RAT cell has been selected, or proceeds to Step ST3310in a case where the inter-RAT cell has not been selected. The UE thathas returned to Step ST3310 repeats the process of Step ST3310, StepST3314 and Step ST3317.

The problems of the twelfth embodiment are described below. As describedabove, the CSG cell is introduced in the LTE and UMTS. However,Non-Patent Document 6 does not disclose how to introduce a CSG cell inthe process of RRC connection re-establishment as a mobile communicationsystem. In addition, there is no suggestion for the problems indicatedin the twelfth embodiment. In order to receive normal service in the CSGcell, the UE needs to be registered in the CSG cell. The UE that hascompleted the registration stores the CSG-ID of the CSG cell that hasregistered in a whitelist in the UE (such as USIM, SIM, memory and CPU).The CSG cell notifies the UEs being served thereby of the CSG-ID or atracking area code (TAC) associated with the CSG-ID as systeminformation. The CSG-ID or TAC is mapped to the system information blocktype 1 (SIB1), which is notified from the CSG cell on the PDSCH usingthe BCCH. Note that the cycle of broadcasting the SIB1 is set at onceevery 20 ms. In order that the UE select the CSG cell as a suitable celland perform location registration or idle state operation for obtainingnormal service, it is required to additionally perform the process ofdetermining whether or not the own UE has been registered in the CSGcell, compared with the case where the non-CSG cell is selected as asuitable cell. In order to determine whether or not the own UE has beenregistered in the CSG cell, it is required to determine whether or notthe CSG-ID (or TAC) broadcast by the CSG cell is identical to the CSG-IDin the whitelist of the own UE.

The RRC connection re-establishment process when a CSG cell isintroduced is described. The process is substantially identical to thatof FIG. 33, and characteristic Step ST3314 is shown in detail in FIG.34. In Step ST3401, the UE determines whether or not the whitelistincludes the CSG-ID. Alternatively, the UE determines whether or not ithas been registered in the CSG cell. In a case where the whitelistincludes the CSG-ID, or in a case where the UE has been registered inthe CSG cell, the UE proceeds to Step ST3402. In a case where thewhitelist includes no CSG-ID, or in a case where the UE has not beenregistered in the CSG cell, the UE proceeds to Step ST3410. In StepST3402, the UE determines whether or not there are cells capable ofbeing a serving cell among the CSG cells from the measurement results ofthe received quality of the neighboring cells. In a case where there aresuch cells, the UE proceeds to Step ST3403. In a case where there are nosuch cells, the UE proceeds to Step ST3410. In Step ST3403, the UEselects the most excellent cell (also referred to as best cell) from thecells that can serve as a serving cell among the CSG cells, based on thereceived quality, from the measurement results of received quality ofneighboring cells, and then proceeds to Step ST3404.

In Step ST3404, the UE receives a physical downlink control channel(PDCC, which is also referred to as L1/L2 signaling channel) of the cellselected in Step ST3403. The UE needs to perform blind detection forreceiving the PDCCH. As a result of the blind detection, the UE receivesthe assignment of BCCH on the PDSCH, and then proceeds to Step ST3405.In Step ST3405, the UE receives the PDSCH in accordance with theassignment for BCCH that has been received in Step ST3404, and thenproceeds to Step ST3406. The BCCH to which the SIB1 is mapped istransmitted on the PDSCH once every 20 ms. In Step ST3405, the UEobtains the SIB1. In Step ST3406, the UE obtains the CSG-ID or TACmapped to the SIB1 obtained in Step ST3405, and then proceeds to StepST3407. While the CSG-ID may be mapped to another system informationdifferent from the SIB1, it is possible to apply the present embodimenteven in such a case.

In Step ST3407, the UE determines whether or not the CSG-ID of the CSGcell that has been obtained in Step ST3406 is identical to the CSG-ID ofthe registered CSG cell stored in the whitelist of the own UE.Accordingly, the UE determines whether or not the CSG cell can serve asa “suitable cell”. That is, in the case where the CSG-ID of the CSG cellis included in the whitelist, the cell can serve as a “suitable cell” asthe registered CSG cell. On the other hand, in the case where the CSG-IDof the CSG cell is not included in the whitelist, the cell cannot serveas a “suitable cell” as the unregistered CSG cell. In the case where theCSG cell is a registered CSG cell, the UE proceeds to Step ST3315 ofFIG. 33. In the case where the CSG cell is an unregistered CSG cell, theUE proceeds to Step ST3408.

In Step ST3408, the UE excludes the CSG cell from the process ofselecting an E-UTRA cell, and then proceeds to Step ST3409. In StepST3409, the UE determines whether or not the timer T311 has ended. As aresult, in a case where the timer has ended (the timer has timed out,completed or expired), the UE proceeds to Step ST3311 of FIG. 33, orreturns to Step ST3402 in a case where the timer has not ended. In StepST3410, the UE determines whether or not there are cells that can serveas a serving cell among the non-CSG cells from the measurement resultsof the received quality of neighboring cells. In a case where there aresuch cells, the UE proceeds to Step ST3411. In a case where there are nosuch cells, the UE proceeds to Step ST3317 of FIG. 33. In Step ST3411,the UE selects the best cell from the cells that can serve as a servingcell among the non-CSG cells, based on the received quality, from themeasurement results of received quality of neighboring cells, and thenproceeds to Step ST3315 of FIG. 33.

As apparent from the above and FIG. 34, it is shown that the time periodrequired for the UE that has a CSG-ID in the whitelist, that is, the UEregistered in any of CSG cells to select the E-UTRA cell may be longerthan the time period required for the UE that does not has a CSG-ID inthe whitelist, that is, the UE that has not been registered in any ofthe CSG cells to select the E-UTRA cell. This phenomenon occurs moreremarkably in a case where the own UE has been registered in the CSGcell (where it is assumed that CSG-ID=10) but the CSG cell (whereCSG-ID=10) is not in the vicinity thereof. In this case, the UEdetermines the “unregistered CSG cell” in Step ST3407 of FIG. 34.Further, the above problem occurs more remarkably in the case where theUE is present in the location where there are a large number of CSGcells in which the UE has not been registered, and the large number ofCSG cells where registration has not been performed have excellentreceived quality and can serve as a serving cell. This is because, inthis case, the process of Step ST3402 to Step ST3409 of FIG. 34 isrepeated until there is no cell that can serve as a serving cell amongthe CSG cells.

The problem described below occurs due to a difference of time periodrequired for selecting a cell between a UE that has a CSG-ID in awhitelist and a UE that does not have a CSG-ID in the whitelist. Asdescribed above, there is a timer (for example, T311) for allowed timefrom the detection of radio link failure, determination of handoverfailure, determination of integrity failure, or determination of RRCconnection reconfiguration failure to the selection of a cell in theE-UTRA. In a case where there is one type of the timer as in thissituation, the case where a timer value is set so as to be suitable forthe UE that has a CSG-ID in the whitelist is considered. In this case,the CSG-ID is not included in the whitelist, and thus the timer is nottimed out though the time period required for cell selection isrelatively short. That is, in Step ST3310 of FIG. 33, the “timer hasended” is determined with an unnecessary delay. This means that therelease of all radio resources, which is performed in Step ST3312 ofFIG. 33, delays unnecessarily. This results in a problem of thereservation of unnecessary resources. In contrast to this, the casewhere a timer value is set so as to be suitable for a UE that does nothave a CSG-ID in the whitelist is considered. On that occasion,considered is a case where the timer is timed out during the cellselection though there still exists a cell that can serve as a servingcell among the CSG cells because the whitelist includes a CSG-ID in thewhitelist and long time period is required for sell selection.

That is, considered is a case where the “timer has ended” is determinedtoo early in Step ST3310 of FIG. 33 or the “timer has ended” isdetermined too early in Step 3409 of FIG. 34. This leads to a problem ofa reduction in possibility of RRC connection re-establishment in thestate where radio bearers, or, radio resources are reserved though theMAC of the UE having the CSG-ID in the whitelist has been reset. Thisleads to a problem that the UE having a CSG-ID in the whitelist changesto the RRC_IDLE state though there are cells having excellent receivedquality in the vicinity thereof, which causes a control delay. Note thatNon-Patent Document 6 does not suggest this problem. In addition, FIG.34 describes the case where the selection of a CSG cell is performedwith a higher priority compared with the selection of a non-CSG cell.However, the above-mentioned problem occurs even when this priority isnot provided. Further, this problem also occurs in introducing a CSGcell in the LTE (E-UTRAN) system as well as introducing a CSG cell inthe W-CDMA (UTRAN, UMTS) system.

The solution to the problems of the twelfth embodiment is describedbelow. This solution is also applicable to the LTE system as well as theW-CDMA system. The twelfth embodiment discloses that different timersare individually provided in accordance with whether or not thewhitelist includes a CSG-ID and are reflected on the UE for solving theabove-mentioned problems. More specifically, disclosed is that thetimers (for example, T311) for the allowed time from the detection ofradio link failure, determination of handover failure, determination ofintegrity failure or determination of RRC connection reconfigurationfailure to the selection of a cell in the E-UTRA are individuallyprovided (T311_with a whitelist and T311_without a whitelist) inaccordance with whether or not the whitelist includes a CSG-ID and arereflected on the UE.

A specific operation example is decried with reference to FIG. 35. Theportions of the same step numbers as those of FIG. 33 are not describedin FIG. 35. Note that FIG. 34 can be used also in FIG. 35. In StepST3501, the UE determines whether or not the whitelist includes aCSG-ID. Alternatively, the UE determines whether or not the UE has beenregistered in the CSG cell. In a case where the whitelist includes aCSG-ID or in the case where the UE has been registered in the CSG cell,the UE proceeds to Step ST3502. In a case where the whitelist include noCSG-ID or in a case where the UE has not been registered in the CSGcell, the UE proceeds to Step ST3503. In Step ST3502, the UE sets, asthe timer (for example, T311) for the allowed time period for thedetection of radio link failure, determination of handover failure,determination of integrity failure or determination of RRC connectionreconfiguration failure to the selection of a cell in the E-UTRA, thetimer (for example, T311_with a whitelist) for the allowed time periodfor the detection of radio link failure, determination of handoverfailure, determination of integrity failure or determination of RRCconnection reconfiguration failure to the selection of a cell in theE-UTRA in the case where the whitelist includes a CSG-ID or in the casewhere a UE has been registered in the CSG cell, and then proceeds toStep ST3307.

In Step ST3503, the UE sets, as the timer (for example, T311) of theallowed time period for the detection of radio link failure,determination of handover failure, determination of integrity failure ordetermination of RRC connection reconfiguration failure to the selectionof a cell in the E-UTRA, the timer (for example, T311_without awhitelist) for the allowed time period for the detection of radio linkfailure, determination of handover failure, determination of integrityfailure or determination of RRC connection reconfiguration failure tothe selection of a cell in the E-UTRA in the case where the whitelistincludes no CSG-ID or in the case where a UE has not been registered inthe CSG cell, and then proceeds to Step ST3307.

Next, the method of notifying different timers individually provided inaccordance with whether or not the whitelist includes a CSG-ID isdisclosed. As a first method, a serving cell (on the network side)notifies the UEs of the timer (for example, T311_with a whitelist) usedin a case where the whitelist includes a CSG-ID as well as the timer(for example, T311_without a whitelist) used in a case where thewhitelist includes no CSG-ID. More specifically, a notification is madewith the use of the dedicated control channel (DCCH) or broadcastcontrol channel (BCHH). In a case of using the DCCH, this is the methodexcellent in that control is enabled in accordance with thecommunication state of the UE. While, in a case where the BCCH is used,this is the method excellent in that all UEs being served can benotified and radio resources are effectively used. As a specific examplein the case where a notification is made with the use of the BCCH,mapping to the MIB or SIB is conceivable.

In the case where the MIB is used, mapping is performed to the PBCH,which is the method excellent in that a UE is capable of receiving asmall amount of control delay. In the case where the SIB is used, anotification is made with the use of the SIB1. This is the methodexcellent in that the MIB or SIB1 is the broadcast information that isthe absolutely required minimum broadcast information received from cellsearch to the idle state operation, and that a control delay of a UE isreduced. In addition, as part of the UE-timer and constants informationelement, mapping is performed to the system information block type 2(SIB2), and a notification is made on the PDSCH using the BCCH. Further,irrespective of whether the serving cell is a CSG cell or a non-CSGcell, the timer (for example, T311_with a whitelist) used in the casewhere the whitelist includes a CSG-ID and the timer (for example,T311_without a whitelist) used in the case where the whitelist includesno CSG-ID are mapped to a system information block type 2 (SIB2) as partof the UE-timer and constants information element, and the serving cell(on a network side) notifies the UEs of the timers on the PDSCH usingthe BCCH. In the case of using the SIB2, a notification can be madesimultaneously with a similar (same type of) parameter in terms oftimer, which is the method excellent in that the UE that has received anotification can perform the process easily. Further, even in the methodof making a notification in the system information other than the SIB1and SIB2, which is also the broadcast information, and thus all UEsbeing served can be notified. Therefore, this is the method excellent inthat radio resources are effectively used. The UE is capable ofobtaining different timers only by receiving the BCCH or DCCH of aserving cell, whereby an effect of control delay prevention can beachieved.

As a second method, a timer (for example, T311_without a whitelist) usedin the case where the whitelist includes no CSG-ID is mapped to the SIB2as part of the UE-timer and constants information element, and theserving cell (on the network side) notifies the UEs of the timer on thePDSCH using the BCCH. Further, irrespective of whether the serving cellis a CSG cell or a non-CSG cell, the timer (for example, T311_without awhitelist) used in the case where the whitelist includes no whitelist ismapped to the SIB2 as part of the UE-timer and constants informationelement, and the serving cell (on the network side) notifies the UEs ofthe timer on the PDSCH using the BCCH. The CSG cell maps the timer (forexample, T311_with a whitelist) used in the case where the whitelistincludes a CSG-ID to the system information and notifies the UEs of thetimer on the PDSCH using the BCCH.

A specific operation example is described with reference to FIG. 36 andFIG. 37. The portions of the same step numbers as those of FIG. 33 andFIG. 35 and the portions of the same step numbers as those of FIG. 34are not described in FIG. 36 and FIG. 37, respectively. In Step ST3601of FIG. 36, the UE determines whether or not the serving cell is a CSGcell. In a case where the serving cell is a CSG cell, the UE proceeds toStep ST3502. In a case where the serving cell is not a CSG cell, the UEproceeds to Step ST3503.

In Step ST3502 of FIG. 36, the UE sets the T311_with a whitelist (T311received from the CSG cell (serving cell)) as the T311. In Step ST3503of FIG. 36, the UE sets the T311_without a whitelist (T311 received fromthe non-CSGL cell (serving cell)) as the T311. In Step ST3701 of FIG.37, the UE determines whether or not the timer (for example, T311_with awhitelist) used in the case where the whitelist includes a CSG-ID hasbeen set as the T311.

In the case where the T311_with a whitelist has been set, the UEproceeds to Step ST3407. In a case where the T311_with a whitelist hasnot been set, the UE proceeds to Step ST3702.

In Step ST3702 of FIG. 37, the UE obtains the T311_with a whitelist fromthe system information mapped to the BCCH on the PDSCH that has beenreceived in Step ST3405 and then proceeds to Step ST3703. In Step ST3703of FIG. 37, the UE sets, as the timer (for example, T311) for theallowed time for the detection of radio link failure, determination ofhandover failure, determination of integrity failure or determination ofRRC connection reconfiguration failure to the selection of a cell in theE-UTRA, the timer (for example, T311_with a whitelist) for the allowedtime for the detection of radio link failure, determination of handoverfailure, determination of integrity failure or determination of RRCconnection reconfiguration failure to the selection of a cell in theE-UTRA in a case where the whitelist includes a CSG-ID or in a casewhere a UE has been registered in the CSG cell, and then proceeds toStep ST3407. The second method is capable of achieving an effect that achange due to the CSG introduction does not need to be added to thesystem information of a non-CSG cell. This does not require a change inthe LTE system (eUTRA/eUTRAN) including no existing CSG, which improvescompatibility.

The method of notifying a timer (for example, T311_with a whitelist)used in a case where the whitelist includes a CSG-ID in the systeminformation mapped to the BCCH on the PDSCH is specifically described inthe second method. Also in the second notification method, the dedicatedcontrol channel and broadcast control channel (MIB, SIB) can be used asa specific example as in the first notification method.

Effects of the twelfth embodiment are described below. UEs that have aCSG-ID in a whitelist and UEs that do not have a CSG-ID in a whitelistmay coexist being served by a base station. A timer (for example, T311)for the allowed time from the detection of radio link failure,determination of handover failure, determination of integrity failure ordetermination of RRC connection reconfiguration failure to the selectionof a cell in the E-UTRA can be set individually in a UE that has aCSG-ID in the whitelist and a UE that does not have a CSG-ID in thewhitelist. This enables appropriate setting of the timer value to a UEthat has a CSG-ID in the whitelist as well as a UE that does not have aCSG-ID in the whitelist. As a result, it is possible to avoid thewasteful reservation of radio resources due to the timer being setlonger, and accordingly an effect that radio resources are usedeffectively can be obtained. In addition, it is possible to achieve aneffect that an increase in control delay as a mobile communicationsystem is avoided due to the timer being set shorter. Owing to theprevention of control delay, an effect that the power consumption of aUE is reduced can be obtained as well.

The solution of the twelfth embodiment is excellent in that theabove-mentioned effects are achieved if a network side (such as a basestation) does not recognize whether or not a relevant UE has a CSG-ID ina whitelist. Through the above, a UE is not required to notify a basestation of the presence or absence of a CSG-ID in the whitelist, whichachieves effective use of radio resources. Further, an effect of areduction in processing load of a base station can be achieved in thatthe base station is not required to manage the presence or absence of aCSG-ID in the whitelist of UEs being served thereby.

Thirteenth Embodiment

Non-Patent Document 7 discloses that in the LTE mobile communicationsystem, the priorities of different E-UTRAN frequencies or inter-RATfrequencies are provided to the UEs from the network side in the systeminformation and the RRC message. In a case where priorities are assignedto the UEs from the network side via dedicated signaling, the UEs ignoreall the priorities provided in the system information. Non-PatentDocument 6 describes the following. In a case where the RRC connectionrelease message includes the idle mode Mobility Control Information andthe idle mode Mobility Control Information includes the cell reselectionpriority expiry timer (for example, T320), the following operation isperformed as a mobile communication system. FIG. 38 shows the processflow as a UE that is disclosed. In Step ST3801, the UE receives thepriorities of different E-UTRAN frequencies or inter-RAT frequencies inthe system information transmitted from the base station, and thenproceeds to Step ST3802. In Step ST3802, the UE determines whether ornot to have received the priorities of different E-UTRAN frequencies orinter-RAT frequencies in a dedicated signal transmitted from the basestation. In a case where they have been received, the UE proceeds toStep ST3803. In a case where they have not been received, the UEproceeds to Step ST3804. In Step ST3803, the UE reselects a cell inaccordance with the priorities received in the system information.

In Step ST3804, the UE reselects a cell in accordance with thepriorities received in a dedicate signal, and then proceeds to StepST3805. In Step ST3805, the UE determines whether or not it has beenaway from the PLMN in which the priorities are set in the dedicatedsignal. The UE proceeds to Step ST3808 in a case where it has been awaytherefrom. The UE proceeds to Step ST3806 in a case where it has notbeen away therefrom. In Step ST3806, the UE determines whether or not ithas changed to the RRC connected state. The UE proceeds to Step ST3808in a case where it has changed. The UE proceeds to Step ST3807 in a casewhere it has not changed. In Step ST3807, the UE determines whether ornot the timer T320 has ended. In a case where the timer T320 has ended,the UE proceeds to Step ST3808. In a case where the timer T320 has notended, the UE returns to Step ST3804 and repeats the process from theStep ST3804 to Step ST3807. Step ST3804 to Step ST3807 are processed inan arbitrary order, and further, may be processed at the same time.

The problem of the thirteenth embodiment is described below. Asdescribed above, a CSG cell is introduced in the LTE and UMTS. Only anon-CSG cell is a target of cell reselection by a UE that has not beenregistered in any CSG cell, that is, a UE that does not have a CSG-ID inthe whitelist. Not only a non-CSG cell but also a CSG cell is a targetof reselection by a UE that has been registered in any CSG cell, thatis, a UE that has a CSG-ID in the whitelist. Further, the frequency(frequency layer) dedicated to a CSG where only CSG cells exist is beingstudied. Therefore, a problem such as an increase in control delay as amobile communication system occurs in a case where the same priorities(priorities of different E-UTRAN frequencies or Inter-RAT frequencies)are set in a UE that has not been registered in a CSG cell (UE that doesnot have a CSG-ID in the whitelist) and a UE that has been registered inany CSG cell (UE that has a CSG-ID in the whitelist). Further, theproblem occurs in introducing a CSG cell in the LTE (E-UTRAN) system aswell as in introducing a CSG cell in the W-CDMA (UTRAN, UMTS) system.

A solution to the problem of the thirteenth embodiment is describedbelow. This solution is applicable to the LTE system as well as theW-CDMA system. The thirteenth embodiment discloses that, in order tosolve the above-mentioned problem, different priorities (such aspriorities of different E-UTRAN frequencies or inter-RAT frequencies)are individually provided in accordance with whether or not thewhitelist includes a CSG-ID to be reflected on a UE. A specificoperation example is described with reference to FIG. 39. The sameportions as those of FIG. 38 are not described in FIG. 39. In StepST3901, the UE receives the priorities (priorities of different E-UTRANfrequencies or inter-RAT frequencies) for a UE that has a CSG-ID in thewhitelist (for a UE that has been registered in a CSG cell) and thepriorities for a UE that does not have a CSG-ID in the whitelist (for aUE that has not been registered in a CSG cell), which are transmittedfrom a base station in the system information, and then proceeds to StepST3802. In Step ST3902, the UE determines whether or not the whitelistincludes a CSG-ID. Alternatively, the UE determines whether or not theUE has been registered in a CSG cell. In a case where the whitelistincludes a CSG-ID, or in a case where the UE has been registered in aCSG cell, the UE proceeds to Step ST3903. In a case where the whitelistincludes no CSG-ID, or in a case where the UE has not been registered ina CSG cell, the UE proceeds to Step ST3904. In Step ST3903, the UEreselects a cell in accordance with the priorities for a UE that has aCSG-ID in the whitelist (for a UE that has been registered in the CSGcell), which has been received in the system information. In StepST3904, the UE reselects a cell in accordance with the priorities for aUE that does not have CSG-ID in the whitelist (for a UE that has notbeen registered in a CSG cell), which has been received in the systeminformation.

In Step ST3905, the UE determines whether or not the whitelist includesa CSG-ID. Alternatively, the UE determines whether or not the UE hasbeen registered in the CSG cell. In a case where the whitelist includesa CSG-ID or in a case where the UE has been registered in the CSG cell,the UE proceeds to Step ST3906. In a case where the whitelist includesno CSG-ID or in a case where the UE has not been registered in a CSGcell, the UE proceeds to Step ST3907. In Step ST3906, the UE reselects acell in accordance with the priorities for a UE that has a CSG-ID in thewhitelist (for a UE that has been registered in a CSG cell), which hasbeen received in the dedicated signal, and then proceeds to Step ST3805.In Step ST3907, the UE reselects a cell in accordance with thepriorities for a UE that does not have a CSG-ID in the whitelist (for aUE that has not been registered in a CSG cell), which has been receivedin a dedicated signal, and then proceeds to Step ST3805. In this case,the priorities that differ depending on whether or not the whitelistincludes a CSG-ID may be any one of the priorities notified in thesystem information or the priorities notified in the dedicated signal.

Next, the method of notifying the priorities that differ depending onwhether or not the whitelist includes a CSG-ID as the system information(Step ST3901) is disclosed. As a first method, the priorities used inthe case where the whitelist includes a CSG-ID and the priorities usedin the case where the whitelist includes no CSG-ID are notified to a UEby a serving cell (on a network side) on the PDSCH using the BCCH as thesystem information. Further, irrespective of whether the serving cell isa CSG cell or a non-CSG cell, the priorities used in the case where thewhitelist includes no CSG-ID are notified to a UE by a serving cell (ona network side) on the PDSCH using the BCCH as the system information.By the first method, the UE is capable of obtaining different prioritiesonly through reception of the BCCH of the serving cell, which achievesthe effect of preventing a control delay. As a second method, thepriorities used in the case where the whitelist includes no CSG-ID arenotified to a UE by a serving cell (on a network side) on the PDSCHusing the BCCH as the system information. Further, irrespective ofwhether the serving cell is a CSG cell or a non-CSG cell, the prioritiesused in a case where the whitelist includes a CSG-ID and the prioritiesused in a case where the whitelist includes no CSG-ID are notified to aUE by the serving cell (on a network side) on the PDSCH using the BCCHas the system information. The priorities used in a case where thewhitelist includes a CSG-ID are notified to the UE on the PDSCH usingthe BCCH by being mapped to the system information by the CSG cell. Thisachieves an effect that a change due to the CSG introduction is notrequired to be added to the system information of a non-CSG cell. As aresult, the LTE system (eUTRA/eUTRAN) including no existing CSG does notneed to be changed, which improves compatibility.

Next, as to the method of notifying the priorities for the case wherethe whitelist includes a CSG-ID or the case where the UE has beenregistered in the CSG cell, and priorities for the case where thewhitelist includes no CSG-ID or the case where the UE has not beenregistered in the CSG cell, which are notified from a base station (on anetwork side) to a UE in a dedicate signal, an RRC message isconceivable.

Effects of the thirteenth embodiment are described below. UEs that havea CSG-ID in the whitelist and UEs that do not have a CSG-ID in thewhitelist may coexist by being served by a base station. The priorities(such as priorities of different E-UTRAN frequencies or inter-RATfrequencies) are allowed to be set individually in a UE that has aCSG-ID in the whitelist and a UE that does not have a CSG-ID to thewhitelist. This achieves an effect of preventing an increase in controldelay as a mobile communication system. The solution of the thirteenthembodiment is excellent in that the above-mentioned effect is achievedeven if the network side (such as a base station) does not recognizewhether or not a relevant UE has a CSG-ID in a whitelist. As a result,the presence or absence of a CSG-ID in the whitelist is not required tobe notified from a UE to a base station, which enables effective use ofradio resources. In addition, an effect of alleviating the processingload of a base station can be achieved in that a base station does notneed to manage the presence or absence of a CSG-ID in the whitelist ofUEs being served thereby.

Fourteenth Embodiment

The problem of the fourteenth embodiment is described below. In aconventional technology, there is one type of effective time of thepriorities (priorities of different E-UTRAN frequencies or inter-RATfrequencies) notified from the network side (base station) to a UE in adedicated signal, as described in the thirteenth embodiment. Asdescribed above, a CSG cell is introduced in the LTE and UMTS. Only anon-CSG cell is a target of the cell reselection by a UE that has notbeen registered in any CSG cell, that is, a UE that does not have aCSG-ID in the whitelist. Accordingly, it is considered that thepriorities change a little. Not only a non-CSG cell but also a CSG cellis a target of the reselection by a UE that has been registered in anyCSG cell, that is, a UE that has a CSG-ID in the whitelist. Therefore,it is considered that the priorities change frequently. If there is onetype of effective time of priorities in a situation where thefrequencies of priority change vary as described above, it is notpossible to set the effective time suitable for each situation change,leading to a problem that a control delay increases. Further, thisproblem also occurs in introducing a CSG cell in the LTE (E-UTRAN)system and introducing a CSG cell in the W-CDMA (UTRAN, UMTS) system.

A solution to the problem of the fourteenth embodiment is describedbelow. This solution is applicable to the LTE system as well as theW-CDMA system. The fourteenth embodiment discloses that, in order tosolve the above-mentioned problem, the effective time (such as T320) ofdifferent priorities (priorities of different E-UTRAN frequencies orinter-RAT frequencies) is individually provided in accordance withwhether or not the whitelist includes a CSG-ID, to be reflected on a UE.A specific operation example is described with reference to FIG. 40. Thesame portions as those of FIG. 38 are not described in FIG. 40. In StepST4001, the UE determines whether or not the whitelist includes aCSG-ID. Alternatively, the UE determines whether or not it has beenregistered in the CSG cell. In the case where the whitelist includes aCSG-ID or in the case where the UE has been registered in the CSG cell,the UE proceeds to Step ST4002. In the case where the whitelist includesno CSG-ID or in the case where the UE has not been registered in the CSGcell, the UE proceeds to Step ST4003. In Step ST4002, the UE sets, asthe effective time (for example, T320) of priorities (priorities ofdifferent E-UTRAN frequencies or inter-RAT frequencies), the effectivetime (for example, T320_with a whitelist) of the priorities (prioritiesof different E-UTRAN frequencies or inter-RAT frequencies) for the casewhere the whitelist includes a CSG-ID or the case where the UE has beenregistered in the whitelist, and then proceeds to Step ST3807.

In Step ST4003, the UE sets, as the effective time (for example, T320)of priorities (priorities of different E-UTRAN frequencies or inter-RATfrequencies), the effective time (for example, T320_without a whitelist)of the priorities (priorities of different E-UTRAN frequencies orinter-RAT frequencies) for the case where the whitelist includes noCSG-ID or the case where the UE has not been registered in the CSG cell,and then proceeds to Step ST3807. As to the method of notifying theeffective time of priorities for the case where the whitelist includes aCSG-ID or the case where the UE has been registered in the CSG cell, andthe effective time of priorities for the case where the whitelistincludes no CSG-ID or the case where the UE has not been registered inthe CSG cell, an RRC message and a broadcast control channel areconceivable. In the case where the dedicated control channel is used,this is the method excellent in that control is enabled in accordancewith the communication state of the UE.

In the case where a notification is made on the broadcast controlchannel, this is the method excellent in that all UEs being served canbe notified and that radio resources are effectively used. Thefourteenth embodiment can be used together with the thirteenthembodiment. As to the method of notifying the effective time ofpriorities for the case where the whitelist includes a CSG-ID or thecase where the UE has been registered in the CSG cell, and the effectivetime of priorities for the case where the whitelist includes no CSG-IDor the case where the UE has not been registered in the CSG cell, theRRC message and broadcast control channel are conceivable. In a casewhere a notification is made in the RRC message, further, it isconceivable to make a notification together with the priorities notifiedin a dedicated signal. In the case where a notification is made in theRRC message, this method is excellent in that the priorities and theeffective time of the priorities can be notified by the samenotification method and that a mobile communication system is avoidedfrom becoming intricate. Further, this method is excellent in that thecontrol delay of a mobile communication system can be reduced bynotifying the priorities as well as the effective time of thepriorities. In the case where a notification is made on the broadcastcontrol channel, this is the method excellent in that all UEs beingserved can be notified and radio resources are effectively used.

The effects of the fourteenth embodiment are described below. UEs thathave a CSG-ID in the whitelist and UEs that do not have a CSG-ID in thewhitelist may coexist by being served by a base station. Setting for theeffective time of the priorities (priorities of different E-UTRANfrequencies or inter-RAT frequencies) is enabled individually for a UEthat has a CSG-ID in the whitelist and a UE that does not have a CSG-IDin the whitelist. This enables the setting for the effective time of thepriorities in accordance with the frequency of a priority change.Accordingly, an effect of preventing an increase in control delay as amobile communication system is achieved.

The solution of the fourteenth embodiment is excellent in that theabove-mentioned effect is achieved even if a network side (such as abase station) does not recognize whether or not a relevant UE has aCSG-ID in the whitelist. As a result, a UE is not required to notify abase station of the presence or absence of a CSG-ID in the whitelist,which achieves effective use of radio resources. In addition, an effectof alleviating the processing load is achieved in that the base stationis not required to manage the presence or absence of a CSG-ID of UEsbeing served thereby. The use of the fourteenth embodiment as well asthe thirteenth embodiment enables highly flexible priority setting thatis suitable for a UE that has a CSG-ID in the whitelist and a UE thatdoes not have a CSG-ID in the whitelist. Accordingly, an effect ofpreventing an increase in control delay as a mobile communication systemis achieved.

Fifteenth Embodiment

Non-Patent Document 6 (Chapter 10.1.1.2) and Non-Patent Document 7(Chapter 5.2.4.2) disclose the process of cell reselection as an LTEmobile communication system. The matters disclosed therein are describedbelow. The UE in an RRC_IDLE state performs cell reselection. The UEperforms measurements on a serving cell and neighbor cells forperforming reselection.

Neighbor cells in the serving cell system information are not requiredto be indicated (in order that a UE perform cell search andmeasurements). The measurements are omitted in a case where thecharacteristics of the serving cell satisfy the measurement criteria. Inthe cell reselection, a cell on which a UE should camp is authenticated.This is based on the cell reselection criteria regarding measurementsfor a serving cell. The reselection on the same frequency is based oncell ranking. The reselection on different frequencies is based on theabsolute priorities where the UE attempts to camp on an availablefrequency having the highest frequency. The absolute priorities forreselection are provided only by the RPLMN that is the PLMN whoselocation has been registered last time, which is effective only withinthe RPLMN. The priorities are provided in the system information and areeffective in all UEs within a cell (UEs by being served by a cell). Theexceptional priorities for each UE can be notified in an RRC connectionrelease message. The effective time can be associated with thepriorities of individual UEs. It is possible to show layer-specific cellreselection parameters (for example, such as layer-specific offsets) forneighbor cells of different frequencies. Those parameters are common toall neighbor cells on the frequency. A neighbor cell list (NCL) can beprovided in order that a serving cell deal with exceptional cases on thesame frequency and different frequencies. The NCL includes cell-specificcell reselection parameters (for example, cell-specific offsets) forspecific neighbor cells. A blacklist can be provided so that a UE willnot reselect specific neighbor cells on the same frequency and differentfrequencies. The cell reselection depends on speed (which is enabled todepend on speed). Speed detection is based on the solution for UTRAN.While it is possible to apply cell reselection parameters to all UEs ofone cell, it is also possible to set specific reselection parameters foreach UE group or each UE.

A process flow as a UE, which is disclosed in FIG. 41, is describedbelow. In Step ST4101, the UE performs cell selection or cellreselection, and then proceeds to Step ST4102. In Step ST4102, the UEdetermines whether or not measurement criteria for starting cellreselection are satisfied. Specifically, the UE determines whether ornot the received quality of a serving cell is equal to or smaller than athreshold. More specifically, the UE determines whether or notS_ServingCell is equal to or smaller than S_intrasearch (orS_ServingCell is equal to or smaller than S_non intrasearch). In a casewhere the measurement criteria are satisfied, the UE proceeds to StepST4103. In a case where the measurement criteria are not satisfied, theUE repeats the process of Step ST4102. In Step ST4103, the UE performsmeasurements for cell reselection, and then proceeds to Step ST4104. InStep ST4104, the UE determines whether or not to perform cellreselection from the results of the measurements performed in StepST4103. In a case of performing cell reselection, the UE returns to StepST4101. In a case of not performing cell reselection, the UE returns toStep ST4102.

A CSG cell is introduced in the LTE and UMTS. It is studied that a moreinexpensive accounting system is set for the CSG cell compared with anon-CSG cell. Therefore, it is expected that a user will attempt to campon a CSG cell in a location that can be selected by a CSG cell. Further,in a situation in which a CSG cell exists within the coverage of anon-CSG cell as a mobile communication system, the processing load of anon-CSG cell is alleviated as the number of UEs that manage schedulingor the like increases.

Accordingly, it is expected that a UE in a location which can beselected by a CSG cell will camp on the CSG cell for a mobilecommunication system as well.

The following problems arise in the above-mentioned cell reselectionprocess described in Non-Patent Document 6 and Non-Patent Document 7.

A case where a CSG cell is installed in a non-CSG cell is considered. Inaddition, a case where a UE whose serving cell is a non-CSG cell existsin the coverage of a CSG cell is considered. The UE does not perform themeasurements for cell reselection in a case where the measurementcriteria of the UE are not satisfied in this situation, in a case wherethe received quality of a serving cell (non-CSG cell) is larger than athreshold, or in a case where S_ServingCell>S_intrasearch. The UEdetermines in Step ST4102 of FIG. 41 that the measurement criteria arenot satisfied, and then repeats Step ST4102 without performing theprocess of Step ST4103. This means that the UE does not gain anopportunity to reselect the CSG cell though it is within the coverage ofa CSG cell. This leads to a problem that a user is unable to benefitfrom an accounting plan for a CSG cell. Further, there arises a problemthat the load of a non-CSG cell cannot be alleviated in a mobilecommunication system as well.

The above-mentioned problems are also disclosed in Non-Patent Document8. Non-Patent Document 8 is the document for UTRA. Non-Patent Document 8discloses the following method as the solution to the above-mentionedproblems. The UE should be able to search for a HNB even in a case wherea serving cell is in a good condition (Sx>S_intrasearch,Sx>S_intersearch). In that case, the HNB search cycle is expected to belonger than a typically used search cycle. Lower power consumption ofthe UE is supported by avoiding search in a place where a HNB is notarranged. Only in a case where the neighbor cell list of a non-CSG cellindicates the existence of the HNB in the neighborhood, a search cyclelonger than a typically used search cycle is used in the method.

The problem of the fifteenth embodiment is described below. Non-PatentDocument 8 is the document for UTRA, and thus Non-Patent Document 8 doesnot disclose the solution to the problem of EUTRAN (LTE system).Further, the neighbor cell list is used for supporting lower powerconsumption of a UE in Non-Patent Document 8. However, it is regarded inthe LTE system that neighbor cells in the serving cell systeminformation do not need to be indicated in order that a UE search forand measure a cell, as described above. Therefore, it is not possible toapply, to the LTE system, the method of supporting lower powerconsumption of a UE using a neighbor cell list, which is described inNon-Patent Document 8, without any change. Further, as a new probleminherent in the technology disclosed in Non-Patent Document 8, even in acase where a CSG cell exists in neighbor cells of a serving cell(non-CSG cell), there is no possibility that the UE may select the CSGcell as a suitable cell when the CSG cell has not been registered in thewhitelist of the UE. Accordingly, there is considered a case where a UEthat has not been registered in the CSG cell starts search using thetechnology of Non-Patent Document 8 even in a case where the servingcell is in a good condition (Sx>S_intrasearch, Sx>S_intersearch) owingto the existence of a CSG cell in neighbor cells of the serving cell(non-CSG cell). In that case, a UE (that has not been registered in aCSG cell) is unable to select a CSG cell, and accordingly measurementsare performed wastefully, leading to a problem of an increase in powerconsumption of a UE.

The solution to the problem of the fifteenth embodiment is describedbelow. The fifteenth embodiment discloses that a cycle (which may be atimer) for performing measurements for cell reselection is provided andreflected on the UE even in a case where a serving cell is in a goodcondition (Sx>S_intrasearch, Sx>S_intersearch), which is applied in acase where the whitelist includes a CSG-ID for solving theabove-mentioned problem. Alternatively, the fifteenth embodimentdiscloses that a cycle (which may be a timer) for performingmeasurements for cell reselection is provided and reflected on a UE evenin a case where a serving cell is in a good condition (Sx>S_intrasearch,Sx>S_intersearch), which is applied in a case where the UE has beenregistered in the CSG cell. A specific operation example is describedwith reference to FIG. 42. The portions of the same step numbers asthose of FIG. 41 are not described in FIG. 42. In Step ST4201, the UEdetermines whether or not the whitelist includes a CSG-ID.Alternatively, the UE determines whether or not it has been registeredin a CSG cell. The UE proceeds to Step ST4202 in a case where thewhitelist includes a CSG-ID, or in a case where it has been registeredin a CSG cell. The UE proceeds to Step ST4207 in a case where thewhitelist includes no CSG-ID or in a case where it has not beenregistered in a CSG cell. In Step ST4202, the UE starts the measurementcycle for cell reselection that is applied in the case where thewhitelist includes a CSG-ID or a timer (for example, T_reselectCSG), andthen proceeds to Step ST4203. Alternatively, the UE starts themeasurement cycle for cell reselection that is applied in the case wherethe UE has been registered in a CSG cell or a timer (for example,T_reselectCSG), and then proceeds to Step ST4203.

In Step ST4203, the UE determines whether or not the measurement cycleis one (for example, T_reselectCSG) for cell reselection that is appliedin the case where a whitelist includes a CSG-ID. Alternatively, the UEdetermines whether or not a timer (for example, T_reselectCSG) for cellreselection, which is applied in the case where the whitelist includes aCSG-ID, has been timed out (or will be timed out). The UE proceeds toStep ST4205 in the case of a measurement cycle or in the case where thetimer has been timed out. The UE proceeds to Step ST4204 in a case wherethe cycle is not a measurement cycle or in a case where the timer hasnot been timed out. In Step ST4204, the UE determines whether or not themeasurement criteria for starting cell reselection are satisfied.Specifically, the UE determines whether or not the received quality of aserving cell is equal to or smaller than a threshold. More specifically,the UE determines whether or not S_ServingCell is equal to or smallerthan S_intrasearch (or S_SearvingCell is equal to or smaller than S_nonintrasearch). The UE proceeds to Step ST4205 in a case where themeasurement criteria are satisfied (in a case where the received qualityof a serving cell is equal to or smaller than the threshold or in a casewhere S_ServingCell≤S_intrasearch). The UE returns to Step ST4203 in acase where the measurement criteria are not satisfied. In Step ST4205,the UE performs measurements for cell reselection, and then proceeds toStep ST4206.

In Step ST4206, the UE determines whether or not to perform cellreselection from the results of measurements performed in Step ST4205.The UE returns to Step ST4101 in a case of performing cell reselection.

The UE returns to Step ST4202 in a case where the UE does not performcell reselection. In Step ST4207, the UE determines whether or not themeasurement criteria for starting cell reselection are satisfied.Specifically, the UE determines whether or not the received quality ofthe serving cell is equal to or smaller than a threshold. Morespecifically, the UE determines whether or not S_ServingCell is equal toor smaller than S_intrasearch (or S_ServingCell is equal to or smallerthan S_non intrasearch). The UE proceeds to Step ST4208 in the casewhere the measurement criteria are satisfied. The UE repeats the processof Step ST4207 in the case where the measurement criteria are notsatisfied. In Step ST4208, the UE performs measurements for cellreselection, and then proceeds to Step ST4209. In Step ST4209, the UEdetermines whether or not to perform cell reselection from the resultsof measurements performed in Step ST4208. The UE returns to Step ST4101in the case of performing cell reselection. The UE returns to StepST4207 in the case of not performing cell reselection.

Next, the method of notifying a cycle (which may be a timer; forexample, T_reselectCSG) for performing measurements for cell reselectioneven in a case where a serving cell is in a good condition(Sx>S_intrasearch, Sx>S_intersearch), which is applied in the case wherea whitelist includes a CSG-ID, is disclosed. As a first method, aserving cell (on a network side) notifies the UE of the cycle on thePBCH or PDSCH using the BCCH as the broadcast information.

Further, the serving cell notifies the cycle on the PBCH using themaster information (MIB) or on the PDSCH using the system information(SIB). The MIB is mapped on the PBCH in the case of using the MIB, whichis the method excellent in that a UE is capable of receiving just asmall amount of control delay. In the case of using the SIB, the cycleis notified using the SIB1. This is the method excellent in that the MIBor SIB1 is the absolutely required minimum broadcast informationreceived for the cell search to the idle state operation and that a UEhas just a smaller amount of control delay. Further, what is used is thebroadcast information even in the method of making a notification in thesystem information other than the SIB1, which is the method excellent inthat all UEs being served can be notified and that radio resources areeffectively used. In the first method, the UE is capable of obtaining acycle (timer) for performing measurements for cell reselection even in acase where the serving cell is in a good condition (Sx>S_intrasearch,Sx>S_intersearch), which is applied in a case where only the BCCH of theserving cell is received and the whitelist includes a CSG-ID, and thusan effect of preventing a control delay can be achieved. As a secondmethod, the CSG cell notifies a UE of the cycle on the PBCH or PDSCHusing the BCCH as the broadcast information. Further, the CSG cellnotifies the cycle on the PBCH using the master information (MIB) or onthe PDSCH using the system information (SIB). In the case of using theMIB, the MIB is mapped on the PBCH, which is the method excellent inthat a UE is capable of receiving just a small amount of control delay.In the case of using the SIB, the cycle is notified using the SIB1. Thisis the method excellent in that the MIB or SIB1 is the absolutelyrequired minimum broadcast information received from the cell search tothe idle state operation and that a UE has just a smaller amount ofcontrol delay. Further, what is used is the broadcast information evenin the method of making a notification in the system information otherthan the SIB1, and thus the cycle can be notified to all UEs beingserved, which is the method excellent in that radio resources areeffectively used. There can be achieved an effect that the systeminformation of a non-CSG cell is not required to be modified due to theCSG. As a result, the LTE system (eUTRA/eUTRAN) including no existingCSG is not required to be modified, which improves compatibility. As athird method, a non-CSG cell notifies a UE on the PBCH or PDSCH usingthe BCCH as the broadcast information. Further, the CSG cell notifiesthe cycle on the PBCH using the master information (MIB) or on the PDSCHusing the system information (SIB). In the case of using the MIB, theMIB is mapped on the PBCH, which is the method excellent in that a UE iscapable of receiving just a small amount of control delay. In the caseof using the SIB, the cycle is notified using the SIB1. This is themethod excellent in that the MIB or SIB1 is the absolutely requiredminimum broadcast information received for the cell search to the idlestate operation and that a UE has just a smaller amount of controldelay. Further, the method of making a notification in the systeminformation other than the SIB1 may be employed. The system informationother than the SIB1 is the broadcast information as well, which is themethod excellent in that all UEs being served can be notified and radioresources are effectively used. It suffices that the parameters arenotified from the non-CSG cell in order that a CSG cell can be selectedwhen a non-CSG cell is the serving cell. Therefore, the third method isexcellent in that radio resources are effectively used. As a fourthmethod, a static value (value known to a UE and a base station as amobile communication system, or value described in, for example,specifications) is set as a mobile communication system. As a result, aradio signal does not occur between a base station (on a network side)and a UE. Accordingly, there can be achieved an effect that radioresources are effectively used. Further, the value is determined in astatic manner, whereby it is possible to achieve an effect thaterroneous reception of a radio signal is prevented.

While it is disclosed above that a cycle (timer) for performingmeasurements for cell reselection is provided to be reflected on a UEeven in a case where the serving cell is in a good condition(Sx>S_intrasearch, Sx>S_intersearch), which is applied in the case wherethe whitelist includes a CSG-ID, different cycles (timers) may beprovided individually in accordance with whether or not the whitelistincludes a CSG-ID to be reflected on a UE, to thereby solve the problem.In addition, while it is disclosed above that a cycle (timer) forperforming measurements for cell reselection is provided to be reflectedon a UE even in a case where the serving cell is in a good condition(Sx>S_intrasearch, Sx>S_intersearch), which is applied in a case wherethe whitelist includes a CSG-ID, the cycle may be applied only in a casewhere the serving cell is a non-CSG cell even in a case of a UE having aCSG-ID in the whitelist. This enables to reduce wasteful measurement(the serving cell is not desired to be changed from a non-CSG cell to aCSG cell, and thus the measurements for selecting a CSG cell also in acase where the received quality of the serving cell is good are wastefulmeasurements) for cell selection in a case where the serving cell hasbeen a CSG cell, which occurs in the above-mentioned solution. Thisachieves an effect that a UE consumes a less amount of power. While theLTE using a HeNB in which a CSG is used is described above, the presentinvention is also applicable to the UMTS using a HNB in which a CSG isused, a HeNB in which a CSG is not used, a HNB, and a base stationhaving a small radius (also referred to as pico cell or macro cell).

Effects of the fifteenth embodiment are described below. UEs that have aCSG-ID in the whitelist and UEs that do have a CSG-ID in the whitelistmay coexist by being served by a base station. By providing a cycle(which may be a timer) for performing measurements for cell reselectioneven in a case where the serving cell is in a good condition(Sx>S_intrasearch, Sx>S_intersearch), which is applied in a case wherethe whitelist includes a CSG-ID, it is possible to solve, in a casewhere the received quality of the serving cell (non-CSG cell) is good, aproblem that a user is unable to benefit from an accounting plan of aCSG cell, which results from the fact that the measurements forreselecting a CSG cell are not performed, and a problem that the load ofa non-CSG cell cannot be alleviated in a mobile communication system aswell. A UE, which performs measurements for cell reselection even in acase where the serving cell is in a good condition (when the measurementcriteria are not satisfied, Sx>S_intrasearch, Sx>S_intersearch), doesnot have a CSG-ID in the whitelist and has not been registered in theCSG cell, does not perform measurements for cell reselection in a casewhere a serving cell is in a good condition (when the measurementcriteria are not satisfied, Sx>S_intrasearch, Sx>S_intersearch) asconventionally. This makes it possible to omit the measurements forselecting a CSG cell even in a case where the serving cell is in a goodcondition, which is wasteful for a UE that is unable to reselect a CSGcell because it has not been registered in the CSG cell. This achievesan effect that the power consumption of a UE that has not beenregistered in a CSG cell is reduced. The effects are the effectsaccording to the present invention, which cannot be achieved by thetechnology disclosed in Non-Patent Document 8. The solution of thefifteenth embodiment is excellent in that the problems can be solvedwithout using a neighbor cell list. This is because a CSG cell, HeNB andHNB are assumed to have a portable size and weight and the CSG cell andthe like are assumed to be installed or removed frequently and flexibly,as described above. Accordingly, in the solution using a neighbor celllist, the neighbor cell list needs to be updated every time the CSGcell, HeNB, HNB and the like are installed or removed, and it isexpected that the neighbor cell list will be updated frequently. As aresult, the mobile communication system becomes intricate andcomplicated in the solution where a neighbor cell list is used. Inaddition, the solution of the fifteenth embodiment is excellent in thatthe above-mentioned effects are achieved even if the network side (suchas a base station) does not recognize whether or not a relevant UE has aCSG-ID in the whitelist. This does not require a UE to notify a basestation of the presence or absence of a CSG-ID in the whitelist, whichenables effective use of radio resources. Further, an effect ofalleviating the processing load of a base station can be achieved inthat a base station is not required to manage the presence or absence ofa CSG-ID in the whitelist of UEs being served thereby.

Next, a first modified example of the fifteenth embodiment is described.In the fifteenth embodiment, a cycle (which may be a timer) forperforming measurements for cell reselection is provided to be reflectedon a UE even in a case where the serving cell is in a good condition(Sx>S_intrasearch, Sx>S_intersearch), which is applied in a case wherethe whitelist includes a CSG-ID, to thereby solve the problems. However,it is unclear that CSG cells existing in the vicinity of a presentserving cell can be a suitable cell just because the whitelist includesa CSG-ID. In a case where a UE has not been registered in a CSG cellexisting in the vicinity of a present serving cell, a problem that thepower consumption of a UE increases occurs by performing themeasurements for cell reselection even when the serving cell is in agood condition. This is a problem occurring when, for example, a userwho has registered in a CSG cell installed in a company goes home.

The solution to the problem of the first modified example of thefifteenth embodiment is described below. The first modified example ofthe fifteenth embodiment discloses, in order to solve theabove-mentioned problem, that an offset is added to the cycle forperforming measurements for cell reselection to be reflected on a UEeven in a case where the serving cell is in a good condition, when acell cannot be selected even though the measurements for cell selectionhave been performed in the cycle (which may be a timer) for performingmeasurements for cell reselection, which is applicable in the case wherethe whitelist includes a CSG-ID, are performed even in a case where theserving cell is in a good condition (Sx>S_intrasearch,Sx>S_intersearch). A specific operation example is described withreference to FIG. 43. The portions of the same step numbers as those ofFIG. 42 are not described in FIG. 43. In Step ST4301, the UE adds anoffset value to the cycle (timer; for example, T_reselectCSG) forperforming measurements for cell reselection even in a case where theserving cell is in a good condition (Sx>S_intrasearch,Sx>S_intersearch), and then proceeds to Step ST4202. For example, if theoffset value is a positive value, in a case where cell reselection hasnot been performed even though measurements for cell reselection havebeen performed even when the serving cell has been in a good condition(Sx>S_intrasearch, Sx>S_intersearch), that is, in a case where a CSGcell that serves as a suitable cell for the UE has not been found, thecycle for performing measurements for cell reselection becomes longereven when the serving cell is in a good condition. Accordingly, thepower consumption of the UE in a case where the UE has not beenregistered in a CSG cell existing in the vicinity of a present servingcell can be reduced with the use of an offset value. The method ofnotifying a cycle (timer) for performing measurements for cellreselection even in a case where the serving cell is in a good state inthe fifteenth embodiment can be used as the method of notifying anoffset value. In this case, the cycle (timer) for performingmeasurements for cell reselection may be notified simultaneously with orindividually of an offset value even in a case where the serving cell isin a good condition.

While the LTE using a HeNB in which a CSG is used is described above,the present invention is also applicable to a UMTS using a HNB in whicha CSG is used, a HeNB in which a CSG is not used, a HNB, and a basestation having a small radius (also referred to as pico cell or macrocell).

The first modified example of the fifteenth embodiment is capable ofachieving the following effect in addition to the effects of thefifteenth embodiment. It is possible to reduce the power consumption ofthe UE in a case where the UE has not been registered in a CSG cellexisting in the vicinity of a present serving cell. The solution of thefirst modified example of the fifteenth embodiment is excellent in thatthe above-mentioned effect is achieved even though a network side (suchas a base station) does not recognize which CSG cell a relevant UE hasbeen registered in (which CSG-ID is included in the whitelist). As aresult, a UE is not required to notify a base station of a CSG-ID in thewhitelist, which achieves effective use of radio resources. In addition,an effect of alleviating the processing load of a base station can beachieved in that a base station does not need to manage a CSG-ID in thewhitelist of UEs being served thereby.

Next, a second modified example of the fifteenth embodiment isdescribed. Another solution to the problem described in the firstmodified example of the fifteenth embodiment, which is different fromthat of the first modified example of the fifteenth embodiment, isdisclosed. The second modified example of the fifteen embodimentdiscloses, in order to solve the above-mentioned problem, that theapplication of the cycle for performing measurements for cellreselection is canceled even in a case where the serving cell is in agood condition, when a cell cannot be selected even though themeasurements for cell selection have been performed in the cycle (whichmay be a timer) for performing measurements for cell reselection, whichis applicable to the case where the whitelist includes a CSG-ID, areperformed even in a case where the serving cell is in a good condition(Sx>S_intrasearch, Sx>S_intersearch). A specific operation example isdescribed with reference to FIG. 44. The portions of the same stepnumbers as those of FIG. 42 are not described in FIG. 44. In StepST4206, the UE determines whether or not cell reselection has beenperformed from the results of the measurements performed in Step ST4205.In a case where cell reselection has been performed, the UE returns toStep ST4101. In a case where cell reselection has not been performed,the UE proceeds to Step ST4207.

While the LTE using a HeNB in which a CSG is used is described above,the present invention is also applicable to a UMTS using a HNB in whicha CSG is used, a HeNB in which a CSG is not used, a HNB, and a basestation having a small radius (also referred to as pico cell or macrocell).

The second modified example of the fifteenth embodiment is capable ofachieving the following effect in addition to the effects of thefifteenth embodiment. It is possible to reduce the power consumption ofthe UE in a case where the UE has not been registered in a CSG cellexisting in the vicinity of a present serving cell. Further, thesolution of the second modified example of the fifteenth embodiment isexcellent in that the above-mentioned effect is achieved even though anetwork side (such as a base station) does not recognize which CSG cella relevant UE has been registered in (which CSG-ID is included in thewhitelist). As a result, a UE is not required to notify a base stationof the presence or absence of a CSG-ID in the whitelist, which achieveseffective use of radio resources. In addition, an effect of alleviatingthe processing load of a base station can be achieved in that a basestation does not need to manage a CSG-ID in the whitelist of UEs beingserved thereby.

Sixteenth Embodiment

A sixteenth embodiment discloses another solution to the problemdescribed in the fifteenth embodiment, which is different from that ofthe fifteenth embodiment. Further, even in a case where the receivedquality of the serving cell that is a non-CSG cell is good in thecurrent cell reselection process, the following operation is conceivableso as to select a CSG cell in neighbor cells. For example, S_intrasearchis set to be low. As a result, even in a case where the received qualityof the serving cell is good, the measurement criteria are satisfied moreeasily, which facilitates the measurements for cell reselection.However, when S_intrasearch is set to be low as described above, even ina case where the received situation of a serving cell is good in all UEs(including a UE that does not have a CSG-ID in a whitelist) being servedby the serving cell, the measurement criteria are satisfied more easily,which facilitates the measurements for cell reselection. In that case,it is not possible to select a CSG cell by a UE (that has not beenregistered in a CSG cell), and thus wasteful measurements are caused,resulting in a problem that the power consumption of a UE increases.

The sixteenth embodiment discloses, in order to solve theabove-mentioned problem, that the measurement criteria for starting cellreselection are provided individually for the case where the whitelistincludes a CSG-ID and a case where the whitelist includes no CSG-ID tobe reflected on a UE. More specifically, the sixteenth embodimentdiscloses that thresholds to be compared with the received quality ofthe serving cell, which are the measurement criteria for starting cellreselection, are provided individually for the case where the whitelistincludes a CSG-ID and a case where the whitelist includes no CSG-ID tobe reflected on a UE. A specific operation example is described withreference to FIG. 45. The portions of the same step numbers as those ofFIG. 41 and FIG. 42 are not described in FIG. 45. In Step ST4201, the UEdetermines whether or not the whitelist includes a CSG-ID.Alternatively, the UE determines whether or not the UE has beenregistered in the CSG cell. The UE proceeds to Step ST4501 in a casewhere the whitelist includes a CSG-ID or in a case where the UE has beenregistered in the CSG cell. The UE proceeds to Step ST4502 in a casewhere the whitelist includes no CSG-ID or in a case where the UE has notbeen registered in the CSG cell. In Step ST4501, the UE determineswhether or not the measurement criteria for cell reselection, which areapplied in the case where the whitelist includes a CSG-ID, aresatisfied. As a specific example, the UE determines whether or not thereceived quality (for example, Sx) of the serving cell is equal to orsmaller than a threshold (for example, S_intrasearchCSG) that is appliedin the case where the whitelist includes a CSG-ID.

The UE proceeds to Step ST4205 in a case where the measurement criteriaare satisfied, as a specific example, in a case whereSx≤S_intrasearchCSG. The UE returns to Step ST4501 in a case where themeasurement criteria are not satisfied, as a specific example, in a casewhere Sx>S_intrasearchCSG. In this case, comparison may be performed notonly with the threshold regarding whether or not the measurementcriteria of the same frequency are satisfied but also with the threshold(for example, S_intersearchCSG) regarding whether or not the measurementcriteria of different frequencies are satisfied. In Step ST4502, the UEdetermines whether or not the measurement criteria for cell reselection,which are normally (may be in a case where the whitelist includes noCSG-ID) applied, are satisfied. As a specific example, the UE determineswhether or not the received quality (for example, Sx) of the servingcell is equal to or smaller than a threshold (S_intrasearch). The UEproceeds to Step ST4208 in a case where the measurement criteria aresatisfied, as a specific example, in a case where Sx≤S_intrasearch. TheUE returns to Step ST4502 in a case where the measurement criteria arenot satisfied, as a specific example, in a case where Sx>S_intrasearch.In this case, comparison may be performed not only with the thresholdregarding whether or not the measurement criteria of the same frequencyare satisfied but also with the threshold (for example, S_intersearch)regarding whether or not the measurement criteria of differentfrequencies are satisfied. Further, a threshold (for example,S_interserachCSG) that is applied in the case where the whitelistincludes a CSG-ID, which is disclosed above, may be applied only in acase where the serving cell is a non-CSG cell even in a UE that has aCSG-ID in the whitelist. This enables to reduce wasteful measurements(the serving cell is not desired to be changed from a non-CSG cell to aCSG cell, and thus measurements for selecting a CSG cell also in a casewhere the received quality of the serving cell is good are wastefulmeasurements) for cell selection in a case where the serving cell hasbeen a CSG cell, which occurs in the above-mentioned solution. Thisachieves an effect that a UE consumes a less amount of power.

The method of notifying the cycle (timer) for performing measurementsfor cell reselection even in a case where the serving cell is in a goodcondition in the fifteenth embodiment can be used as the method ofnotifying the measurement criteria for starting cell reselection in acase where the whitelist includes a CSG-ID. In this case, themeasurement criteria for starting cell reselection in a case where thewhitelist includes a CSG-ID may be notified simultaneously with orindependently of the measurement criteria for cell reselection that arenormally applied.

While the LTE using a HeNB in which a CSG is used is described above,the present invention is also applicable to a UMTS using a HNB in whicha CSG is used, a HeNB in which a CSG is not used, a HNB, and a basestation having a small radius (also referred to as pico cell or macrocell).

The effects of the sixteenth embodiment is described below. UEs thathave a CSG-ID in a whitelist and UEs that do not have a CSG-ID in awhitelist may coexist by being served by a base station. By providingthe measurement criteria for starting cell reselection, which areapplied in a case where the whitelist includes a CSG-ID, it is possibleto solve, in a case where the received quality of the serving cell(non-CSG cell) is good, a problem that a user is unable to benefit froman accounting plan of a CSG cell, which results from the fact that themeasurements for reselecting a CSG cell are not performed as well as aproblem that the load of a non-CSG cell cannot be alleviated in a mobilecommunication system as well. A UE, which performs measurements for cellreselection even in a case where the serving cell is in a good conditionwhen the whitelist includes a CSG-ID, does not have a CSG-ID in thewhitelist and has not been registered in a CSG cell, does not performmeasurements for cell reselection in a case where the serving cell is ina good condition as conventionally. This makes it possible to omit themeasurements for selecting a CSG cell even in a case where the servingcell is in a good condition, which is wasteful for a UE that is unableto reselect a CSG cell because it has not been registered in the CSGcell. This achieves an effect that the power consumption of a UE thathas not been registered in a CSG cell is reduced. This effect is theeffect according to the present invention, which cannot be achieved bythe technology disclosed in Non-Patent Document 8.

The solution of the sixteenth embodiment is excellent also in that theproblem can be solved without using a neighbor cell list. This because,as described above, the CSG cell, HeNB and HNB are assumed to have aportable size and weight and the CSG cell and the like are assumed to beinstalled or removed frequently and flexibly. Accordingly, the neighborcell list needs to be updated every time the CSG cell, HeNB, HNB and thelike are installed or removed in the solution in which the neighbor celllist is used, and it is expected that the neighbor cell list will beupdated frequently. This is because the mobile communication systembecomes intricate and complicated in the solution where a neighbor celllist is used. Further, the solution of the sixteenth embodiment isexcellent in that the above-mentioned effect is achieved even though anetwork side (such as a base station) does not recognize whether or nota relevant UE has a CSG-ID in the whitelist. As a result, the UE is notrequired to notify the base station of the presence or absence of aCSG-ID in the whitelist, which achieves effective use of radioresources. In addition, an effect of alleviating the processing load ofa base station can be achieved in that the base station does not need tomanage the presence or absence of a CSG-ID in the whitelist of UEs beingserved thereby.

Next, a first modified example of the sixteenth embodiment describedabove is described. Specifically, the solution to the problem describedin the first modified example of the fifteenth embodiment is disclosed.The first modified example of the sixteenth embodiment discloses, inorder to solve the above-mentioned problem, that the application of themeasurement criteria (for example, S_intrasearchCSG) for starting cellreselection is canceled, even though the measurements for cell selectionare performed in accordance with the measurement criteria (for example,S_intrasearchCSG) for starting cell reselection, which are applied in acase where the whitelist includes a CSG-ID, in a case where a cell hasnot been selected.

A specific operation example is described with reference to FIG. 45. InStep ST4206, the UE determines whether or not the cell reselection hasbeen performed from the results of the measurements performed in StepST4205. The UE returns to Step ST4101 in the case where cell reselectionhas been performed. The UE proceeds to Step ST4502 in the case wherecell reselection has not been performed.

Seventeenth Embodiment

3GPP is studying base stations referred to as Home-NodeB (Home-NB, HNB)and Home-eNodeB (Home-eNB, HeNB). HNB/HeNB is a base station for, forexample, household, corporation or commercial access service inUTRAN/E-UTRAN. Non-Patent Document 9 discloses three different modes ofthe access to the HeNB and HNB. Those are an open access mode, a closedaccess mode and a hybrid access mode. The respective modes have thefollowing characteristics. In the open access mode, the HeNB and HNB areoperated as a normal cell of an operator. In the closed access mode, theHeNB and HNB are operated as a CSG cell. The CSG cell is a cell whereonly CSG members are allowed access. In the hybrid access mode, the HeNBand HNB are CSG cells where non-CSG members are allowed access at thesame time. In other words, a cell in the hybrid access mode is the cellthat supports both the open access mode and the closed access mode. Thecell of hybrid access mode is also referred to as a hybrid cell.

3GPP is studying the method of allowing cell reselection to a desiredCSG cell even in a case where the received quality of the serving cellis good. It is considered that the above needs to be studied also in thehybrid cell. For example, Non-Patent Document 10 proposes that UEs of aCSG member should stay longer at hybrid cells than UEs of a non-CSGmember, and that a camping mechanism is required to vary between UEs ofa CSG member and the UEs of non-CSG member. However, Non-Patent Document10 has no description on a specific method therefor.

The hybrid cell is a CSG cell, and thus the methods disclosed in thefifteenth embodiment, first modified example of the fifteenthembodiment, second modified example of the fifteenth embodiment,sixteenth embodiment and first modified example of the sixteenthembodiment are applicable as a specific method of causing UEs of a CSGmember to stay longer at the hybrid cells than UEs of a non-CSG member.Those methods enable the UE having a CSG-ID in the whitelist (CSG-IDlist, allowed CSG list) or the UE registered in a CSG cell to executethe process of cell reselection more rapidly compared with the otherUEs. Accordingly, it is possible to detect CSG cells including a hybridcell rapidly. This allows a UE having a CSG-ID of the CSG to which thehybrid cell belongs or a UE registered in the CSG to perform cellreselection to the hybrid cell rapidly. The methods disclosed in theembodiments above are applicable also to a specific operation.

The sixteenth embodiment discloses that the measurement criteria forcell reselection are provided individually for the case where thewhitelist includes a CSG-ID and a case where the whitelist includes noCSG-ID. As an example, the threshold of cell reselection in the casewhere the whitelist includes no CSG-ID is regarded as S_intrasearch andthe threshold of cell reselection in the case where the whitelistincludes a CSG-ID is regarded as S_intrasearchCSG.

In order that the process of cell reselection be performed more rapidlyin the case where the whitelist includes a CSG-ID than the case wherethe whitelist includes no CSG-ID, S_intrasearchCSG may be set to belower than S_intrasearch (S_intrasearch>S_intrasearchCSG). The processof cell reselection is started more easily as the threshold of cellreselection becomes smaller, which accordingly facilitates cellreselection to a CSG cell by a UE of a CSG member. Accordingly, cellreselection to a hybrid cell is facilitated in the seventeenthembodiment as well.

Eighteenth Embodiment

Even in a case where the received quality of the serving cell is good,for example, Non-Patent Document 11 describes the method of providingQoffset for each CSG cell as a specific method of enabling cellreselection to a desired CSG cell.

Qoffset is the offset provided to the measured value of received qualityof the detected cell when cell ranking is performed in cell reselection,as described in Non-Patent Document 7. Qoffset is broadcast from theserving cell together with the information of a cell to which theQoffset is provided.

Further, Non-Patent Document 12 describes the method of providing oneQoffset to hybrid cells, that is, the method of providing one Qoffset toall cells in a hybrid access mode. Further, described is the method ofproviding two Qoffsets corresponding to a macro cell RSRP range, andQoffsets are individually applied when macro cell RSRP is below or abovean RSRP threshold.

As described in those methods, offset values are varied only for eachcell, each cell type, or positional relationship with a macro cell onlyby providing Qoffset for each CSG cell, providing one Qoffset to hybridcells, or providing Qoffset correspondingly to a macro cell RSRP range.

However, while the hybrid cell is a CSG cell, it supports both an openaccess mode and a closed access mode at the same time. For this reason,the criteria for cell reselection cannot be varied between UEs of anon-CSG member and UEs of a CSG member for a hybrid cell. Accordingly,those methods cause a problem that UEs of a CSG member are not allowedto stay longer at hybrid cells than UEs of a non-CSG member.

In order to solve the above-mentioned problem, in the presentembodiment, there are provided an offset value (Qoffset_csg) applied toUEs having a CSG-ID in the whitelist or UEs registered in a CSG and anoffset value (Qoffset_noncsg) applied to the other UEs.

As described above, it is possible to vary the criteria for cellreselection between UEs of a non-CSG member and UEs of a CSG member byproviding offsets individually for UEs having a CSG-ID in the whitelistor UEs registered in a CSG and the other UEs. This enables UEs of a CSGmember to stay longer at hybrid cells than UEs of a non-CSG member.

A specific operation example is described with reference to FIG. 46. Theportions of the same step numbers as those of FIG. 41 are not describedin FIG. 46. In Step ST4103, the UE performs measurements for cellreselection and performs cell ranking. In Step ST4601, the UE determineswhether or not the whitelist includes a CSG-ID. Alternatively, the UEdetermines whether or not the UE has been registered in a CSG cell. TheUE proceeds to Step ST4602 in a case where the whitelist includes aCSG-ID or in a case where the UE has been registered in a CSG cell. InStep ST4602, the UE subtracts Qoffset_csg from the measured value. TheUE proceeds to Step ST4603 in the case where the whitelist includes noCSG-ID or in the case where the UE has not been registered in a CSGcell. In Step ST4603, the UE subtracts Qoffset_noncsg from the measuredvalue. The UE performs cell ranking based on the results obtained by thesubtraction, whereby it is possible to vary the measurement criteria forperforming cell reselection between UEs having a CSG-ID in the whitelistor UEs registered in a CSG and the other UEs. It is also possible toperform cell ranking only in Step ST4602 or Step ST4603 and omit cellranking in Step ST4103.

As to the value of Qoffset_noncsg and the value of Qoffset_csg, itsuffices that the received quality criteria for cell reselection besatisfied more rapidly in the UEs having a CSG-ID in the whitelist orUEs registered in a CSG than the other UEs, in accordance with the radiowave environments of a serving cell and neighbor cells.

For example, the value of Qoffset_csg is set to be smaller than thevalue of Qoffset_noncsg (Qoffset_noncsg>Qoffset_csg). This makes theresults calculated in consideration of those offsets for one cell becomelarger in the UEs having a CSG-ID in the whitelist or UEs registered ina CSG than the other UEs. Accordingly, the UEs having a CSG-ID in thewhitelist or the UEs registered in a CSG satisfy the received qualitycriteria for sell reselection more rapidly than the other UEs. As aresult of the received quality criteria for cell reselection beingsatisfied more rapidly, reselection to a suitable cell is enabled morerapidly. Therefore, it is possible to allow the UEs of a CSG member toperform cell reselection more rapidly than UEs of a non-CSG member forhybrid cells, which enables UEs of a CSG member to stay longer than UEsof a non-CSG member.

The criteria for cell ranking may be expressed by equations below.

As to the UEs having a CSG-ID in the whitelist or the UEs registered ina CSG,Rn=Qmeas,n−Qoffset_csg,while as to the other UEs,Rn=Qmeas,n−Qoffset_noncsg.

Qmeas and n represent measured values of received quality of an n-thcell, and Rn represents calculation results of received quality inconsideration of offset.

Alternatively, the criteria for cell ranking may be expressed byequations below.

As to the UEs having a CSG-ID in the whitelist or the UEs registered ina CSG,Rn=Qmeas,n−Qoffset−Qoffset_csg,while as to the other UEs,Rn=Qmeas,n−Qoffset−Qoffset_noncsg.

Considering conventional Qoffset, Qoffset_noncsg and Qoffset_csg can beused only for difference between the UEs having a CSG-ID in a whitelistor the UEs registered in a CSG and the other UEs.

The first method to the fourth method disclosed as the method ofnotifying a cycle for performing measurements for cell reselection inthe fifteenth embodiment are applicable as the method of notifyingQoffset_csg and Qoffset_noncsg. Similar effects can be achieved in thecases where those are applied.

Further, in the first method, a notification may be made using an SIB4in a case where an SIB is used.

Conventional offset values are transmitted together with the informationof corresponding cells in the SIB4. The offset values are transmittedtogether with those pieces of information, and accordingly the cellranking criteria are executed for each corresponding cell together withthe conventional offset values. As the information of correspondingcell, a PCI range capable of being provided for hybrid cells may beused. This enables to set the same value to a plurality of hybrid cells,which reduces the information amount of the SIB4.

Further, in the second method, only the hybrid cells may notify offsetvalues as the broadcast information.

In the method disclosed above, the offset value (Qoffset_csg) applied tothe UEs having a CSG-ID in the whitelist or the UEs registered in a CSGand the offset value (Qoffset_noncsg) applied to the other UEs areprovided, so that cell ranking is performed and then cell reselection isperformed.

As another method, a value (Qoffset_delta) of a difference between theoffset value applied to the UEs having a CSG-ID in the whitelist or theUEs registered in a CSG and the offset value applied to the other UEsmay be provided. That is, Qoffset_noncsg and Qoffset_delta may beprovided to be used as the criteria for cell ranking.

For example, the criteria for cell ranking may be expressed by equationsbelow.

As to the UEs having a CSG-ID in the whitelist or the UEs registered ina CSG,Rn=Qmeas,n−(Qoffset_noncsg−Qofffset_delta),while as to the other UEs,Rn=Qmeas,n−Qoffset_noncsg.

As a result, similar effects to those of the method of notifyingQoffset_noncsg and Qoffset_csg, which is disclosed above, can beachieved.

Further, as still another method, an offset value applied to the UEshaving a CSG-ID in the whitelist or the UEs that have not beenregistered in a CSG may be set as the conventional Qoffset to be usedtogether with the difference value Qoffset_delta.

For example, the criteria for cell ranking may be expressed by equationsbelow.

As to the UEs having a CSG-ID in the whitelist or the UEs registered ina CSG,Rn=Qmeas,n−(Qoffset−Qofffset_delta),while as to the other UEs,Rn=Qmeas,n−Qoffset.

As a result, not only similar effects to those of the method disclosedabove can be achieved, but also parameters to be set can be reduced byone. That is, both Qoffset_csg and Qoffset_noncsg are not required to beset, and only Qoffset_delta needs to be set. Accordingly, it is possibleto reduce the information amount for parameter setting. Theabove-mentioned method is applicable as the notification method. Asanother method, Qoffset and Qoffset_delta may be notified individuallyfrom different cells. For example, Qoffset is notified from a servingcell, while Qoffset_delta is notified from a hybrid cell. Qoffset_deltais a value used only for a hybrid cell, and thus it may be notified onlyfrom hybrid cells, so that the UEs having a CSG-ID in the whitelist orthe UEs registered in a CSG may perform recalculation using the offsetvalue (Qoffset_delta) in the criteria for cell ranking. The other UEsare not required to perform recalculation and receive the offset valueof a hybrid cell, whereby it suffices that only the received quality ismeasured. This can simplify the measurements in cell reselection, and aneffect of reducing power consumption of a UE can be obtained.

The method disclosed in the present embodiment is also applicable to themethod of providing Qoffset for each CSG cell that is described inNon-Patent Document 11, the method of providing one Qoffset to hybridcells that is described in Non-Patent Document 12, or the method ofproviding two Qoffsets corresponding to an RSRP range of a macro celland individually applying each Qoffset when macro cell RSRP is below orabove an RSRP threshold. For example, those Qoffsets may be used asQoffset of the criteria for cell ranking that is disclosed in thepresent embodiment, or used in addition to Qoffset. As a result, it ispossible to taken into consideration respective Qoffsets that areprovided for each CSG cell, are specific to hybrid, or correspond to theRSRP range of a macro cell.

Further, as another method, the values described in those Non-PatentDocuments are avoided to be applied, as the offset values applied to theUEs having a CSG-ID in the whitelist or the UEs registered in a CSG, tothe other UEs. For example, the values described in those Non-PatentDocuments may be used in Qoffset_delta as the criteria for cell ranking.This enables the criteria for cell reselection to vary between the UEsof a non-CSG member and the UEs of a CSG member for hybrid cells.

It is possible to use the method disclosed in the present embodiment incombination with the method disclosed in the fifteenth embodiment, thefirst modified example of the fifteenth embodiment, the second modifiedexample of the fifteenth embodiment, the sixteenth embodiment, the firstmodified example of the sixteenth embodiment or the seventeenthembodiment.

For example, FIG. 47 shows a specific operation example in a case of thecombination with the fifteenth embodiment. The portions of the same stepnumbers as those of FIG. 42 are not described in FIG. 47. In StepST4201, the UE determines whether or not the whitelist includes aCSG-ID. Alternatively, the UE determines whether or not the UE has beenregistered in the CSG cell. In the case where the whitelist includes aCSG-ID or in the case where the UE has been registered in the CSG cell,in Step ST4701, the UE subtracts Qoffset_csg from the measured value. Ina case where the whitelist includes no CSG-ID or in a case where the UEhas not been registered in the CSG cell, in Step ST4702, the UEsubtracts Qoffset_noncsg from the measured value. As a result of thecell ranking performed based on the results obtained by the subtraction,it is possible to vary the determination criteria for performing cellreselection between the UEs having a CSG-ID in the whitelist or the UEsregistered in a CSG and the other UEs. It is also possible to performcell ranking only in Step ST4701 or Step ST4702, and omit the cellranking in Step ST4205 or Step ST4208.

It is possible to use the other embodiment or modified example incombination through similar operations. As a result of the combinationof the method disclosed in the present embodiment and the embodiment ormodified example, there is obtained an effect that flexible handling isalso available for a difference in the environment of respective radiowaves that results from a flexible arrangement of HeNBs or HNBsincluding hybrid cells.

The method disclosed in the present embodiment enables the criteria forcell reselection to vary between the UEs of a non-CSG member and the UEsof a CSG member for hybrid cells. As a result, the UEs of a CSG memberare allowed to stay longer at the hybrid cells than the UEs of a non-CSGmember.

Accordingly, the CSG members are capable of obtaining service such ashigh-speed communications and preferential charging plan, which isdedicated to CSG members in hybrid cells, more rapidly in a longerperiod of time.

Nineteenth Embodiment

The eighteenth embodiment discloses the method in which the UEs of a CSGmember perform cell reselection on hybrid cells more rapidly than theUEs of a non-CSG member, in other words, the method of facilitating(inbound) reselection to hybrid cells.

In order that the UEs of a CSG member perform cell reselection from thehybrid cells more slowly than the UEs of a non-CSG member, in otherwords, in order to make (outbound) cell reselection from the hybridcells difficult, the present embodiment discloses the case of applyingthe method of providing an offset value (Qoffset_csg) applied to the UEshaving a CSG-ID in the whitelist or the UEs registered in a CSG and anoffset value (Qoffset_noncsg) applied to the other UEs, and performingcell ranking and cell reselection with the use of those, to thereby varythe criteria for cell reselection between the UEs of a non-CSG memberand the UEs of a CSG member.

As a specific operation example, criteria for cell ranking may beexpressed by equations below.

As to the UEs having a CSG-ID in the whitelist or the UEs registered ina CSG,Rs=Qmeas,s+Qhyst−Qoffset_csg,while as to the other UEs,Rs=Qmeas,s+Qhyst−Qoffset_noncsg.

Qmeas and s represent the measured values of the received quality of aserving cell, Qhyst represents an offset value for providing hysteresis,and Rs represents the calculation results of the received quality of aserving cell in which the offset is taken into consideration.

A hybrid cell serves as a serving cell in the reselection from thehybrid cells. Accordingly, in order to make the cell reselection fromthe hybrid cells difficult, a difference is provided in the measurementvalue of the serving cell between the UEs having a CSG-ID in thewhitelist or the UEs registered in a CSG and the other UEs in cellranking during cell reselection. As a specific example, calculation isperformed with the use of Qoffset_noncsg and Qoffset_csg in Rsderivation. This enables the determination criteria for performing cellreselection from hybrid cells to vary between both UEs.

As to the value of Qoffset_noncsg and the value of Qoffset_csg, the UEshaving a CSG-ID in the whitelist or the UEs registered in a CSG may beset so as to satisfy the received quality criteria for cell reselectionmore slowly than the other UEs, in accordance with the environment ofradio waves of the serving cell and neighbor cells.

For example, the value of Qoffset_csg is set to be larger than the valueof Qoffset_noncsg (Qoffset_noncsg<Qoffset_csg). Accordingly, the resultscalculated in consideration of the offsets for the serving cell that isa hybrid cell are lower in the UEs having a CSG-ID in the whitelist orthe UEs registered in a CSG than the other UEs. This means that the UEshaving a CSG-ID in the whitelist or the UEs registered in a CSG satisfythe received quality criteria for cell reselection more slowly than theother UEs.

As a result of the received quality criteria being satisfied moreslowly, it is possible to prevent the reselection from hybrid cells frombeing performed before the received quality criteria are satisfied. Thisenables the UEs of a CSG member to perform cell reselection at hybridcells more slowly than the UEs of a non-CSG member, which makes itpossible for the UEs of a CSG member to stay longer than the UEs of anon-CSG member.

FIG. 48 shows a specific operation example of cell reselection at hybridcells. The portions of the same step numbers as those of FIG. 41 are notdescribed in FIG. 48. The UE that has started the process of cellselection or cell reselection in Step ST4101 performs measurements of aserving cell for cell reselection, and performs cell ranking criteriafor the serving cell. In Step ST4801, the UE determines whether or notthe whitelist includes a CSG-ID. Alternatively, the UE determineswhether or not the UE has been registered in a CSG cell. In the casewhere the whitelist includes a CSG-ID or in the case where the UE hasbeen registered in a CSG cell, the UE proceeds to Step ST4802. In StepST4802, the UE subtracts Qoffset_csg from the measured value. In thecase where the whitelist includes no CSG-ID or in the case where the UEhas not been registered in a CSG cell, the UE proceeds to Step ST4803.In Step ST4803, the UE subtracts Qoffset_noncsg from the measured value.In Step ST4102, the UE determines whether the measurement criteria forcell reselection are satisfied based on those results obtained by thesubtraction. This enables the determination criteria for performing cellreselection to vary between the UEs having a CSG-ID in the whitelist orthe UEs registered in a CSG and the other UEs.

It is also possible to avoid the use of the offset values (Qoffset_csg,Qoffset_noncsg) in derivation of a measured value of a serving cell in acase where cell ranking is performed including the received qualitymeasured value of the serving cell in Step ST4103. In a case where thoseoffset values are not used, the UEs of a CSG member are highly likely toselect a serving cell.

Alternatively, an offset value (Qoffset_csg_r) applied to the UEs havinga CSG-ID in the whitelist or the UEs registered in a CSG and an offsetvalue (Qoffset_noncsg_r) applied to the other UEs may be providedseparately, and in performing the derivation of the measured values of aserving cell when cell ranking is performed including the measured valueof the received quality of the serving cell in Step ST4103, those may beapplied to the measured values of the serving cell to perform cellranking and then perform cell reselection. In this case,Qoffset_noncsg_r is preferably set to be higher than Qoffset_csg_r.Accordingly, the results calculated in consideration of those offsetsfor the serving cell that is a hybrid cell are higher in the UEs havinga CSG-ID in the whitelist or the UEs registered in a CSG than the otherUEs. Therefore, the UEs having a CSG-ID in the whitelist or the UEsregistered in a CSG are highly likely to select a serving cell than theother UEs.

As a result of the criteria for cell ranking being set as describedabove, the UEs of a CSG member are allowed to perform cell reselectionmore slowly than the UEs of a non-CSG member in hybrid cells, whichenables the UEs of a CSG member to stay longer at the hybrid cells thanthe UEs of a non-CSG member.

The first to fourth methods, which are disclosed in the fifteenthembodiment as the method of notifying the cycle for performingmeasurements for cell reselection, are applicable to the method ofnotifying those parameters, and similar effects can be obtained.

Through the combination of the present embodiment and the eighteenthembodiment, it is possible to make the reselection to the hybrid cellseasier and make the reselection from hybrid cells more difficult in theUEs of a CSG member than the UEs of a non-CSG member. Accordingly, it ispossible to allow the UEs of a CSG member to stay longer at the hybridcells than the UEs of a non-CSG member.

In the case where the present embodiment and the eighteenth embodimentare combined, the offset value provided for making the reselection tothe hybrid cells easier and the offset value provided for making thecell reselection from the hybrid cells more difficult in the UEs of aCSG member than the UEs of a non-CSG member may be set to valuesdifferent from each other or the same value.

For example, the respective values are set such that the offset valuesprovided for making the reselection are to the hybrid cells easier areQoffset_csg_in and Qoffset_noncsg_in and the offset values provided formaking the cell reselection from the hybrid cells more difficult areQoffset_csg_out and Qoffset_noncsg_out. As a result, it is possible tocope with more flexible installation and handling of HeNBs and HNBs.

As an example of setting to the same value, two offsets of Qoffset1 andQoffset2 may be provided. In order to make the reselection to the hybridcells easier, Qoffset_csg is set to Qoffset1 and Qoffset_noncsg is setto Qoffset2 to be used in the derivation of a cell ranking Rn ofneighbor cells. On the other hand, in order to make the cell reselectionfrom the hybrid cells more difficult, Qoffset_csg is set to Qoffset2 andQoffset_noncsg is set to Qoffset1 to be used in the derivation of a cellranking Rs of serving cells. Qoffset1 may be set to be lower thanQoffset2. This reduces the number of parameters, leading to a reductionin information amount to be transmitted to the UEs.

The notification methods disclosed in the fifteenth embodiment and theeighteenth embodiment can be used as the method of notifying thoseparameters, and the combination of various notification methods areallowed.

For example, Qoffset_csg_in and Qoffset_noncsg_in may be notified fromthe serving cell on the SIB4 for being used in the derivation of thecell ranking Rn of neighbor cells, whereas Qoffset_csg_out andQoffset_noncsg_out may be notified only from the hybrid cells on theSIB1 for being used in the derivation of the cell ranking Rs of servingcells in the hybrid cells.

This reduces the information amount notified from the cells which arenot hybrid cells.

In a case where two offsets of Qoffset1 and Qoffset2 are provided, anotification may be made on the SIB1 of all cells. As a result, it ispossible to reduce the information amount to be notified also in thehybrid cells.

The method disclosed in the present embodiment can be used incombination with the method disclosed in the fifteenth embodiment, thefirst modified example of the fifteenth embodiment, the second modifiedexample of the fifteenth embodiment, the sixteenth embodiment, the firstmodified example of the sixteenth embodiment, the seventeenth embodimentor the eighteenth embodiment.

Through the combination of the method disclosed in the presentembodiment and the above-mentioned embodiment or modified example, it ispossible to make the reselection to the hybrid cells easier and make thereselection from the hybrid cells more difficult in the UEs of a CSGmember than the UEs of a non-CSG member even in various environments ofradio waves that result from a flexible arrangement of the HeNBs or HNBsincluding hybrid cells. Accordingly, it is possible to allow the UEs ofa CSG member to stay longer at the hybrid cells than the UEs of anon-CSG member.

Twentieth Embodiment

The embodiment above discloses the method of reselecting a cell to/fromthe hybrid cells for allowing the UEs of a CSG member to stay longer atthe hybrid cells than the UEs of a non-CSG member. The presentembodiment discloses the method of handover (inbound HO/outbound HO)to/from the hybrid cells for allowing the UEs of a CSG member to staylonger at the hybrid cells than the UEs of a non-CSG member.

In the handover to/from hybrid cells, the process, rule and criteria ofthe handover are varied between the UEs of a non-CSG member and the UEsof a CSG member. As a specific method, as to the parameters used in HOto/from hybrid cells, the parameters applied to the UEs having a CSG-IDin the whitelist or the UEs registered in a CSG and the parametersapplied to the other UEs are provided. By setting the parameters todifferent values between the UEs of a non-CSG member and the UEs of aCSG member, it is possible to vary the criteria for handover to/fromhybrid cells between the UEs of a non-CSG member and the UEs of a CSGmember.

Examples of parameters used in handover to/from hybrid cells includeparameters serving as indicators for determining whether or not an eventoccurs in a measurement report. That includes thresholds of eventoccurrence (Thresh, Thresh1, Thresh2), an offset value (Ocs) of aserving cell that is applied to the measurement results of the receivedquality, an offset value (Ofs) of the frequency of a serving cell thatis applied to the measurement results of the received quality, an offsetvalue (Ocn) of neighbor cells that is applied to the measurement resultsof the received quality, an offset value (Ofn) of the frequency ofneighbor cells that is applied to the measurement results of thereceived quality, an offset value (Off) for each event and a hysteresis(Hys) for each event.

For example, as to the threshold of event occurrence, Thresh_csg appliedto the UEs having a CSG-ID in a whitelist or the UEs registered in a CSGand Thresh_noncsg applied to the other UEs are provided in a case wherethe serving cell is a hybrid cell. By setting Thresh_csg higher thanThresh_noncsg, event for handover occurs in the UEs of a CSG member moreslowly than the UEs of a non-CSG member, which enables the UEs of a CSGmember to stay longer at the hybrid cells than the UEs of a non-CSGmember.

For example, as to the offset values of neighbor cells, Ocn_csg appliedto the UEs having a CSG-ID in the whitelist or the UEs registered in aCSG and Ocn_noncsg applied to the other UEs are provided. In a casewhere the offset value is subtracting from the measurement results ofthe received quality, Ocn_noncsg is set higher than Ocn_csg. In a casewhere the neighbor cells are hybrid cells, the UEs of a CSG membercalculate the received quality of the neighbor cells using Ocn_csg, andthe UEs of a non-CSG member calculate the received quality of theneighbor cells using Ocn_noncsg. Ocn_noncsg is set higher than Ocn_csg,and thus event for handover occurs more rapidly in the UEs of a CSGmember than the UEs of a non-CSG member, which enables the handover tothe hybrid cells rapidly.

As to the method of notifying the parameters, the parameters may benotified individually from the serving cell to the UEs that performsmeasurement. For example, the parameters may be notified by beingincluded in a measurement control message. As a result, the respectiveUEs can perform setting individually, and setting can be performedindividually in accordance with the situation of radio waves of the UEs,whereby it is possible to obtain excellent communication quality of therespective UEs.

Alternatively, prior to the measurements in the UEs, a differencebetween the parameter applied to the UEs having a CSG-ID in thewhitelist or the UEs registered in a CSG and the parameter applied tothe other UEs may be broadcast from the serving cell as the broadcastinformation.

Any one of the parameters may be notified dedicatedly to the UEs so thatderivation is performed using the difference value. This reduces theinformation notified dedicatedly to the UEs, which reduces the resourceload for signaling.

Still alternatively, the difference value may be preliminarilydetermined in a static manner such that a base station as well as a UEcan recognize the information in advance. There is no need to broadcastthe difference as the broadcast information, which further reduces theresource load for signaling.

The method disclosed in the present embodiment enables the UEs of a CSGmember to perform HO more rapidly than the UEs of a non-CSG member inthe handover to the hybrid cells and the UEs of a CSG-member to performhandover more slowly than the UEs of a non-CSG member in the handoverfrom the handover to the hybrid cells. This allows the UEs of a CSGmember to stay longer at the hybrid cells than the UEs of a non-CSGmember.

The method disclosed in the present embodiment is applicable also in thecase where the serving cell does not recognize whether the UE makesaccess in an open mode or a closed mode, and also in such a case,similar effects can be achieved.

It is possible to use the method disclosed in the present embodiment incombination with the method disclosed in the fifteenth embodiment, thefirst modified example of the fifteenth embodiment, the second modifiedexample of the fifteenth embodiment, the sixteenth embodiment, the firstmodified example of the sixteenth embodiment, the seventeenthembodiment, the eighteenth embodiment or the nineteenth embodiment.

Through the combination of the method disclosed in the presentembodiment and the above-mentioned embodiment or modified example, it ispossible to allow the UEs of a CSG member to stay longer at the hybridcells than the UEs of a non-CSG member irrespective of the UE state,that is, even when the UE is not only in the RRC_Idle state but also inthe RRC_Connected state.

Twenty-First Embodiment

The problem of the present embodiment is described below. For example,there is conceivable the service in which the same owner posses thecells having the same CSG-ID, the cells having the same CSG-ID offer thesame charging benefit, or the cells having the same CSG-ID offer thesame benefit at a communication speed. As a result, the user may desireto reselect the cell having the same CSG-ID.

In order to solve this problem, in the present embodiment, an offsetvalue (Qoffset_samecsg) adaptable to neighbor cells having the sameCSG-ID as that of the serving cell and an offset value (Qoffset_diffcsg)adaptable to neighbor cells having a CSG-ID different from that of theserving cell are provided.

The offsets are individually provided for the neighbor cells having thesame CSG-ID as that of the serving cell and the neighbor cells having aCSG-ID different from that of the serving cell are provide as describedabove, whereby it is possible to vary the criteria for cell reselectionbetween the neighbor cells having the same CSG-ID and the neighbor cellshaving a different CSG-ID. This enables to more easily reselect the cellhaving the same CSG-ID as that of the serving cell compared with thecell having a CDG-ID different therefrom.

A specific operation example is described with reference to FIG. 46. Theportions of the same step numbers as those of FIG. 41 are not describedin FIG. 46. In Step ST4103, the UE performs measurements for cellreselection and performs cell ranking. In Step ST4601, the UE determineswhether or not the CSG-ID of the neighbor cell where measurements havebeen performed is the same as that of the serving cell. In a case ofdetermining that the CSG-ID is the same, the UE proceeds to Step ST4602.In Step ST4602, the UE subtracts Qoffset_samecsg from the measuredvalue. In a case of determining that the CSG-ID is different, the UEproceeds to Step ST4603. In Step ST4603, the UE subtractsQoffset_diffcsg from the measured value. Cell ranking is performed basedon those results obtained by the subtraction, whereby it is possible tovary the measurement criteria for performing cell reselection betweenthe neighbor cells having the same CSG-ID and the neighbor cells havinga different CSG-ID. It is also possible to perform cell ranking only inStep ST4602 or Step ST4603 and omit cell ranking in Step ST4103.

As to the value of Qoffset_samecsg and the value of Qoffset_diffcsg, thecell having the same CSG-ID as that of the serving cell is more likelyto satisfy the received quality criteria for reselection than the cellhaving a CSG-ID different therefrom, in accordance with the environmentof radio waves of the serving cell and the neighbor cells.

For example, the value of Qoffset_samecsg is set to be smaller than thevalue of Qoffset_diffcsg (Qoffset_diffcsg>Qoffset_samecsg). As a result,the cell having the same CSG-ID as that of the serving cell is morelikely to satisfy the received quality criteria for reselection than thecell having a CSG-ID different therefrom. The received quality criteriais more likely to be satisfied, which facilitates the reselection of acell having the same CSG-ID.

The criteria for cell ranking may be expressed by equations below.

As to the neighbor cells having the same CSG-ID as that of the servingcell,Rn=Qmeas,n−Qoffset_samecsg,while as to the neighbor cells having a CSG-ID different from that ofthe serving cell,Rn=Qmeas,n−Qoffset_diffcsg.

Qmeas and n represent the measured values of received quality of an n-thcell, and Rn represents the calculation results of received quality inwhich the offset is taken into consideration.

Further, the Qoffset_samecsg and Qoffset_diffcsg may be set such thatonly the UEs having a CSG-ID in the whitelist or the UEs registered in aCSG are adaptable thereto. The UEs that have not been registered in aCSG do not desire to reselect the cell having the same CSG-ID. Thisalleviates the wasteful processing load of the UEs that have not beenregistered in a CSG, and accordingly an effect of reducing powerconsumption of the UEs can be achieved.

Alternatively, the criteria for cell ranking may be expressed byequations below.

As to the neighbor cells having the same CSG-ID as that of the servingcell,Rn=Qmeas,n−Qoffset−Qoffset_samecsg,while as to the neighbor cells having a CSG-ID different from that ofthe serving cell,Rn=Qmeas,n−Qoffset−Qoffset_diffcsg.

Qoffset_samecsg and Qoffset_diffcsg can be used only for providing adifference between the case of the same CSG-ID as that of the servingcell and the case of the CSG-ID different from that of the serving cell,in consideration of the conventional Qoffsets.

As the method of notifying Qoffset_samecsg and Qoffset_diffcsg, thefirst method to the fourth method that are disclosed as the method ofnotifying the cycle for performing measurements for cell reselection inthe fifteenth embodiment can be applied.

In a case where those are applied, similar effects can be achieved.

Further, in the first method, a notification may be made using the SIB4in the case of using an SIB.

In the SIB4, the conventional offset values are transmitted togetherwith the information of the corresponding cell. As a result of theoffset values being transmitted together with the information, cellranking criteria can be executed together with the conventional offsetvalues for each corresponding cell.

In the method disclosed above, the offset value (Qoffset_samecsg)applied to the neighbor cells having the same CSG-ID as that of theserving cell and the offset value (Qoffset_diffcsg) applied to theneighbor cells having a CSG-ID different from that of the serving cellare provided, so that cell ranking is performed using those and cellreselection is performed.

As another method, there may be provided a difference value(Qoffset_delta2) between the offset value applied to the neighbor cellshaving the same CSG-ID as that of the serving cell and the offset valueapplied to the neighbor cells having a CSG-ID different from that of theserving cell. That is, Qoffset_diffcsg and Qoffset_delta2 may beprovided to be used in the criteria for cell ranking.

For example, the criteria for cell ranking may be expressed as equationsbelow.

As to the neighbor cells having the same CSG-ID as that of the servingcell,Rn=Qmeas,n−(Qoffset_diffcsg−Qoffset_delta2),while as to the neighbor cells having a CSG-ID different from that ofthe serving cell,Rn=Qmeas,n−Qoffset_diffcsg.

As a result, similar effects to those of the method of notifyingQoffset_samecsg and Qoffset_diffcsg, which is disclosed above, can beachieved.

As still another method, the offset value applied to the neighbor cellshaving a CSG-ID different from that of the serving cell may be set asthe conventional Qoffset to be used together with the difference valueQoffset_delta2.

For example, the criteria for cell ranking may be expressed as equationsbelow.

As to the neighbor cells having the same CSG-ID as that of the servingcell,Rn=Qmeas,n−(Qoffset−Qoffset_delta2),while as to the neighbor cells having a CSG-ID different from that ofthe serving cell,Rn=Qmeas,n−Qoffset.

As a result, it is possible not only to achieve similar effects to thoseof the method disclosed above, but also to reduce the parameters to beset by one. That is, both Qoffset_samecsg and Qoffset_diffcsg are notrequired to be set, and it suffices that Qoffset_delta2 is set.Therefore, it is possible to reduce the information amount for parametersetting. The above-mentioned methods are applicable as the notificationmethod. As another method, Qoffset and Qoffset_delta2 may be notifiedindividually from different cells. For example, Qoffset is notified fromthe serving cell while Qoffset_delta2 is notified from the CSG cell.Qoffset_delta2 is the value used only for the CSG cells, and thus it maybe notified only from the CSG cells and, in the criteria for cellranking, recalculation may be performed using the offset value(Qoffset_delta2) for the neighbor cells having the same CSG-ID as thatof the serving cell. Recalculation is not required for non-CSG cells,and it suffices that the received quality is measured. This enables tosimplify the measurements in cell reselection, and an effect of reducingpower consumption of a UE is achieved.

The method disclosed in the present embodiment is also applicable to themethod of providing Qoffset for each CSG cell that is described inNon-Patent Document 11, the method of providing one Qoffset to hybridcells that is described in Non-Patent Document 12, or the method ofproviding two Qoffsets corresponding to an RSRP range of a macro celland applying each Qoffset when macro cell RSRP is below or above an RSRPthreshold. For example, those Qoffsets may be used as Qoffsets in thecriteria for cell ranking disclosed in the present embodiment or may beused in addition to Qoffsets. This also enables to take intoconsideration each Qoffset that is, for example, provided for each CSGcell, is specific to hybrid or corresponds to the RSRP range of a macrocell.

It is possible to use the method disclosed in the present embodiment incombination with the method disclosed in the fifteenth embodiment, thefirst modified example of the fifteenth embodiment, the second modifiedexample of the fifteenth embodiment, the sixteenth embodiment, the firstmodified example of the sixteenth embodiment, the seventeenthembodiment, the eighteenth embodiment, the nineteenth embodiment or thetwentieth embodiment.

For example, a specific operation example in a case of the combinationwith the fifteenth embodiment is described with reference to FIG. 47.The portions of the same step numbers as those of FIG. 42 are notdescribed in FIG. 47. In Step ST4201, the UE determines whether or notthe whitelist includes a CSG-ID. Alternatively, the UE determineswhether or not the UE has been registered in a CSG cell. The UE executesStep ST4701 in the case where the whitelist includes a CSG-ID or in thecase where the UE has been registered in a CSG-ID. In Step ST4701, theUE subtracts Qoffset_samecsg from the measured value in the case wherethe CSG-ID of the neighbor cell where measurements have been performedis the same as that of the serving cell. On the other hand, in StepST4701, the UE subtracts Qoffset_diffcsg from the measured value in thecase where the CSG-ID has been determined to be different from that ofthe serving cell. The UE performs cell ranking based on those results ofthe distraction. In Step ST4702, the UE executes especially nothing inthe case where the whitelist includes no CSG-ID or the case where the UEhas not been registered in a CSG cell. This enables to vary thedetermination criteria for performing cell reselection between theneighbor cells having the same CSG-ID and the neighbor cells having adifferent CSG-ID.

It is possible to use the other embodiment or modified example incombination through similar operations. The method disclosed in thepresent embodiment is combined with the above-mentioned embodiment ormodified example, whereby there is achieved an effect of enablingflexible handling of a difference in environment of respective radiowaves that results from a flexible arrangement of HeNBs or HNBs.

The method disclosed in the present embodiment enables the determinationcriteria for performing cell reselection between the neighbor cellshaving the same CSG-ID and the neighbor cells having a different CSG-ID.As a result, the cells having the same CSG-ID as that of the servingcell can be more likely to be reselected than the cells having a CSG-IDdifferent therefrom. This allows a user to select the cells having thesame CSG-ID continuously, whereby the user can receive the same serviceof the same CSG-ID. Therefore, an effect of the construction of a mobilecommunication system easily used by a user can be achieved.

Twenty-Second Embodiment

In order that a CSG member be able to receive the service such ashigh-speed communications and preferential charging plan for the CSGmember in the hybrid cells more rapidly in a longer period of time, theUEs of a CSG member are required to stay longer at hybrid cells than theUEs of a non-CSG member.

FIG. 49 is a conceptual diagram in a case where the UEs of a CSG memberare caused to stay longer at hybrid cells than the UEs of a non-CSGmember. In the figure, 4901 denotes a non-CSG cell, which is a macrocell (eNB) here. 4902 denotes the coverage of the non-CSG cell 4901.4903 denotes a HeNB in a hybrid access mode, that is, a hybrid cell.4904 denotes the coverage that can be accessed in an open access mode aswell as a closed access mode by the hybrid cell 4903. 4905 denotes thecoverage accessed only in the closed access mode by the hybrid cell4903. 4906 denotes the UE of the same CSG member as the CSG to which thehybrid cell 4903 belongs. 4907 denotes the UE of a non-CSG member. TheUE 4906 of the CSG member communicates with the non-CSG cell 4901outside the area of the coverage 4905, and the UE 4906 that has moved tothe area of the coverage 4905 communicates with the hybrid cell 4903 bycell reselection. The UE 4907 of the non-CSG member still communicateswith the non-CSG cell 4901 also in the area of the coverage 4905, and isallowed to communicate with the hybrid cell 4903 by sell reselectiononly after moving to the coverage 4904.

As described above, when the UEs of a CSG member are caused to staylonger than the UEs of a non-CSG member in the reselection to a hybridcell or from a hybrid cell, the coverage only in the closed access modebecomes wider than the coverage in the open access mode in some cases.In the above-mentioned case, if the initial transmission power of the UEin starting uplink communication at a hybrid cell is the same betweenthe UEs of a CSG member and the UEs of a non-CSG member, the coveragethat can be accessed by the UEs of a CSG member becomes wider,increasing a possibility that the uplink transmission of the UEs of aCSG member may fail.

The process in starting uplink communication includes a random access(RA) procedure. PRACH is used as a physical channel in the RA procedure.The PRACH preamble is used in the initial transmission of PRACH. Theinitial transmission power Pprach of PRACH is determined as follows(Non-Patent Document 13, Non-Patent Document 14).Pprach=min{Pcmax,PREAMBLE_RECEIVED_TARGET_POWER+PL}_[dBm]Pcmax=min{Pemax,Pumax}

where PREAMBLE_RECEIVED_TARGET_POWER represents the target receivedpower of a base station, PL represents path loss, Pemax represents themaximum permissible power that is set for each cell, and Pumaxrepresents the maximum transmission power of a UE. Pemax is the maximumpermissible power that is notified to the UEs as, for example, thebroadcast information from each cell and is common to all UEs beingserved. Pumax is determined in advance correspondingly to a power classof each UE.

As can be seen from the derivation equation for the initial transmissionpower Pprach of PRACH, the initial transmission power is limited byPcmax in a case of, for example, large PL. Pcmax is limited by Pemax aswell, which means that the initial transmission power of PRACH islimited by Pemax. Pemax is common to all UEs being served by the cell,which has the same value for the UEs of a CSG member as well as the UEsof a non-CSG member in a hybrid cell. Accordingly, in a case where thePRACH initial transmission power is limited by Pemax, such as the caseof large PL, the UEs of a CSG member as well as the UEs of a non-CSGmember cannot perform transmission exceeding the common Pemax.Therefore, there is a high possibility that in hybrid cells, the uplinktransmission of the UEs of a CSG member may fail in a case where thecoverage that can be accessed by the UEs of a CSG member becomes widercompared with the UEs of a non-CSG member.

This problem arises in any state of the RRC_Idle state and RRC_Connectedstate. For example, in the RRC_Idle state, this problem arises in a casewhere the UE of a CSG member performs cell reselection to the hybridcell, while in the RRC_Connected state, this problem arises in a casewhere the UE of a CSG member performs HO to the hybrid cell. Thisproblem is not described in any prior art document nor discussed by3GPP.

The present embodiment discloses, in order to solve this problem, themethod capable of varying the initial transmission power of a UE instarting uplink communication between the UEs of a CSG member and theUEs of a non-CSG member. As a specific example, in order to vary theinitial transmission power of PRACH between the UEs of a CSG member andthe UEs of a non-CSG member, the maximum permissible power used inderivation of the PRACH initial transmission power is individuallyprovided for the UEs of a CSG member and the UEs of a non-CSG member inthe hybrid cell. The maximum permissible power for a CSG member isrepresented by Pemax_csg, whereas the maximum permissible power for anon-CSG member is represented by Pemax_noncsg.

The derivation equation of the initial transmission power Pprach in ahybrid cell is expressed as follows.Pprach=min{Pcmax,PREAMBLE_RECEIVED_TARGET_POWER+PL}_[dBm]

As to the CSG member, Pcmax=min{Pemax_csg, Pumax}, while as to thenon-CSG member, Pcmax=min{Pemax_noncsg, Pumax}.

As a result, it is possible for the initial transmission power Pprach ina hybrid cell to have the maximum permissible power different betweenthe UEs of a CSG member and the UEs of a non-CSG member in a case of,for example, large PL. In a case where the coverage of the UEs of a CSGmember becomes wider compared with the UEs of a non-CSG member in thehybrid cell, it is possible to reduce the uplink transmission failure ofthe UEs of a CSG member by setting Pemax_csg larger than Pemax_noncsg.

Further, it is possible to vary the initial transmission power for eachcell in the both UEs by providing the maximum permissible power for eachcell individually for the UEs of a CSG member and the UEs of a non-CSGmember. This enables the flexible arrangement of hybrid cells as asystem and accordingly enables handling of an increase in the number ofHeNBs to be operated in the future.

The method of deriving the uplink initial transmission power in thehybrid cell, which is disclosed here, is applicable in starting uplinkcommunication in the hybrid cell in a case where, for example, the UE ofa CSG member performs cell reselection to the hybrid cell in theRRC_Idle state. Further, the method is applicable in starting uplinkcommunication in the hybrid cell to be targeted in a case where, forexample, the UE of a CSG member executes HO to the hybrid cell in theRRC_Connected state.

The method of notifying the UEs of the maximum permissible power used inthe hybrid cell is described below.

As a first method, the above-mentioned maximum permissible power isnotified from the cell in which the power is set to the UEs being servedthereby on the PBCH or PDSCH using the BCCH as the broadcastinformation. The maximum permissible power is notified on the PBCH usingthe master information (MIB) or on the PDSCH using the systeminformation (SIB). The MIB is mapped on the PBCH, and accordingly themethod in which the MIB is used is excellent in that a UE is capablereceiving just a small amount of control delay. In the case of using theSIB, the maximum permissible power is notified using the SIB1. This isthe method excellent in that the MIB or SIB1 is the absolutely requiredminimum amount of broadcast information received in a time period fromthe start of cell search to entering the idle state (RRC-Idle state) andthat the control delay of a UE is reduced. Further, the maximumpermissible power is notified using the channel for transmitting thebroadcast information even in the method of notifying the power in thesystem information other than the SIB1, which is the method excellent inthat all UEs being served can be notified and that radio resources areeffectively used.

As a second method, the above-mentioned maximum permissible power isdedicatedly notified to the UEs that perform HO from the serving cell inperforming HO on the cell in which the power is set as the target cell.The maximum permissible power may be notified, to the UEs, by beingincluded in the information of the target cell that is required forperforming HO or may be notified using another message. It is possibleto reduce the number of necessary messages as a result of the maximumpermissible power being notified by being included in the information ofthe target cell, which reduces the time period required for completingHO. On the other hand, in a case of notifying the maximum permissiblepower using the another message, the message can be notified only in thecase of the cell that requires setting of the maximum permissible power.Accordingly, in a case of HO to the cell that does not require thesetting of the maximum permissible power, it is possible to reduce theinformation amount that is required for the notification and reduce thenumber of messages.

The value of the maximum permissible power (Pemax_csg) for a CSG memberand the value of the maximum permissible power (Pemax_noncsg) for anon-CSG member may be determined by a hybrid cell or may be determinedby the network side (such as MME and HeNBGW). In the case of thedetermination by the network side, the maximum permissible power isnotified in advance form the network side to the hybrid cell. Thisnotification can be made using the interface S1 of the hybrid cell andthe network side.

Through the determination by the network side, the values can be setbased on the environment of radio waves of the neighbor cells and loadcondition (for example, the number of connected users) thereof. Thisenables reductions in the condition in which communications cannot bemade, connection delay due to erroneous communication, an increase ofsignaling amount, load concentration and the like.

In the above-mentioned methods, the maximum permissible power for a CSGmember is represented by Pemax_csg, whereas the maximum permissiblepower for a non-CSG member is represented by Pemax_noncsg. As anothermethod, a maximum permissible power (Pemax_common) common to the CSGmember and non-CSG member may be provided and a difference (Pemax_delta)of the maximum permissible power between the CSG member and non-CSGmember may be provided. An example of the derivation equation for theinitial transmission power Pprach in the hybrid cell on this occasion isexpressed as follows.Pprach=min{Pcmax,PREAMBLE_RECEIVED_TARGET_POWER+PL}_[dBm]

As to the CSG member, Pcmax=min{Pemax_common+Pemax_delta, Pumax}, whileas to the non-CSG member, Pcmax=min{Pemax_common, Pumax}. This enablesthe UEs of a CSG member and the UEs of a non-CSG member to havedifferent maximum permissible power, and accordingly similar effects tothose of the above-mentioned methods are achieved.

Note that Pemax set as the conventional maximum permissible power may bethe common parameter Pemax_common. As a result, the method of derivingthe initial transmission power of a non-CSG member does not need to bechanged from the current method. Therefore, an effect of preventing amobile communication system from becoming intricate can be achieved.

Further, as another method, Pumax may be provided individually for a CSGmember and a non-CSG member. Pumax represents the maximum transmissionpower of a UE, which is determined in advance in accordance with thepower class of each UE. Pumax may be determined in advance for a CSGmember (Pumax_csg) and a non-CSG member (Pumax_noncsg) in accordancewith the power class of each UE. An example of the derivation equationfor the initial transmission power Pprach in the hybrid cell on thisoccasion is expressed as follows.Pprach=min{Pcmax,PREAMBLE_RECEIVED_TARGET_POWER+PL}_[dBm]

As to the CSG member, Pcmax=min{Pemax, Pumax_csg}, while as to thenon-CSG member, Pcmax=min{Pemax, Pumax_noncsg}.

Accordingly, Pemax can be set to be common to all UEs being served, andthus what is required is the setting little different from theconventional setting.

A static value may be taken as a mobile communication system. The staticvalue refers to a value known to a UE and a base station as a mobilecommunication system and a known value described in a specification. Aradio signal does not occur between a base station (on a network side)and a UE with the use of a static value. Accordingly, an effect can beachieved in that radio resources are effectively used. Further, thestatic value is a value determined in a static manner, with the resultthat an effect of preventing erroneous reception of a radio signal fromoccurring can be achieved.

Described below is a specific operation example in a case where themaximum permissible power for a CSG member is set as Pemax_csg and themaximum permissible power for a non-CSG member is set as Pemax_noncsg inhybrid cells.

FIG. 50 shows an example of the process until the PRACH initialtransmission in hybrid cells.

First, the UE of a CSG member is described. In Step ST5001, the UE of aCSG member camps on the hybrid cell after, for example, cellreselection. The hybrid cell transmits the broadcast information in StepST5004, and the UE of a CSG member receives the broadcast information.The broadcast information includes the maximum permissible power. In acase where uplink transmission occurs in the UE of a CSG member in StepST5005, the UE proceeds to Step ST5007, and derives the uplink initialtransmission power using the maximum permissible power for the UE of aCSG member (Pemax_csg). The UE of a CSG member sets the uplink initialtransmission power to the transmission power in Step ST5009 and thenstarts the uplink transmission in Step ST5011.

Next, the UE of a non-CSG member is described. In Step ST5002, the UE ofa non-CSG member camps on a hybrid cell after, for example, cellreselection. The hybrid cell transmits the broadcast information in StepST5004, and the UE of a non-CSG member receives the broadcastinformation. The broadcast information includes the maximum permissiblepower. In a case where uplink transmission occurs in the UE of a non-CSGmember in Step ST5006, the UE proceeds to Step ST5008, and derives theuplink initial transmission power using the maximum permissible powerfor the UE of a non-CSG member (Pemax_noncsg). The UE of a non-CSGmember sets the uplink initial transmission power to the transmissionpower in Step ST5010 and then starts the uplink transmission in StepST5012.

Note that the timing at which uplink transmission occurs differs foreach UE, and accordingly the timing of uplink initial transmissiondiffers for each UE. Therefore, for example, Step ST5012 may be executedsubsequently to Step ST5011 as shown in the figure, or Step ST5011 maybe executed subsequently to Step ST5012.

As described above, the maximum permissible power used for deriving theuplink initial transmission power is varied in accordance with whetherthe UE that is camping on the hybrid cell belongs to a CSG member or anon-CSG member, whereby it is possible to increase the transmissionpower of uplink transmission for the UE of a CSG member even in a casewhere the UE of a CSG member camps on the area that can be accessed.This enables to secure the uplink received power sufficient forcommunications in hybrid cells.

The method disclosed in the present embodiment enables to solve aproblem that the uplink transmission of the UEs of a CSG member fails ina case where the coverage of the UEs of a CSG member becomes widercompared with the UEs of a non-CSG member in hybrid cells.

In addition, it is possible for the UEs of a CSG member to stay longerat hybrid cells than the UEs of a non-CSG member, and accordingly theCSG member can receive the service such as high-speed communications andpreferential charging plan for the CSG member in hybrid cells morerapidly in a longer period of time.

Further, it is possible to provide lower maximum permissible power tothe UEs of a non-CSG member compared with the UEs of a CSG member, andthus the UEs of a non-CSG member can be prevented from being providedwith transmission power larger than necessary in a case of large PL,which enables to reduce the uplink interference power.

Twenty-Third Embodiment

In order to allow the initial transmission power of the UE when startinguplink communication to vary between the UEs of a CSG member and the UEsof a non-CSG member, in the present embodiment, the criteria differencebetween the UEs having a CSG-ID in the whitelist or the UEs registeredin a CSG and the other UEs in cell reselection.

As a specific example, a difference between the threshold(S_intrasearch) for cell reselection in case where the whitelistincludes no CSG-ID and the threshold (S_intrasearchCSG) for cellreselection in a case where the whitelist includes a CSG-ID or the UEhas been registered in a CSG, which are disclosed in the seventeenthembodiment, is used.

Further, as another specific example, a difference between the offsetvalue (Qoffset_csg_in) applied to the UEs having a CSG-ID in thewhitelist or the UEs registered in a CSG and the offset value(Qoffset_noncsg_in) applied to the other UEs, which are disclosed in theeighteenth embodiment, is used. This difference may be the differencevalue (Qoffset_delta).

Further, as still another specific example, a difference between theoffset value (Qoffset_csg_out) applied to the UEs having a CSG-ID in thewhitelist or the UEs registered in a CSG and the offset value(Qoffset_noncsg_out) applied to the other UEs, which are disclosed inthe nineteenth embodiment, is used. This difference may be a differencevalue.

It suffices that those difference values are used as the differencevalues of the maximum permissible power used in deriving the PRACHinitial transmission power in hybrid cells between the UEs of a CSGmember and the UEs of a non-CSG member.

In the case of the threshold (S_intrasearch) for cell reselection whenthe whitelist includes no CSG-ID and the threshold (S_intrasearchCSG)for cell reselection when the whitelist includes a CSG-ID, which aredisclosed in the seventeenth embodiment, this difference is used. Thedifference value is S_intrasearch_delta.S_intrasearch_delta=S_intrasearch−S_intrasearchCSG

This value is Pemax_delta (=Pemax_csg−Pemax_noncsg) that is a differencevalue of the maximum permissible power used in deriving the PRACHinitial transmission power between the UEs of a CSG member and the UEsof a non-CSG member.

The value may be expressed byPemax_delta=S_intrasearch_deltaorPemax_delta=|S_intrasearch_delta|.

In the case of the offset value (Qoffset_csg_in) applied to the UEshaving a CSG-ID in the whitelist or the UEs registered in a CSG and theoffset value (Qoffset_noncsg_in) applied to the other UEs, which aredisclosed in the eighteenth embodiment, taking the difference value asQoffset_delta (=Qoffset_noncsg_in−Qoffset_csg_in), the value may beexpressed byPemax_delta=Qoffset_deltaorPemax_delta=|Qoffset_delta|.

In the case of the offset value (Qoffset_csg_out) applied to the UEshaving a CSG-ID in the whitelist or the UEs registered in a CSG and theoffset value (Qoffset_noncsg_out) applied to the other UEs, which aredisclosed in the nineteenth embodiment, taking the difference value asQoffset_delta (=Qoffset_csg_out−Qoffset_noncsg_out), the value may beexpressed byPemax_delta=Qoffset_deltaorPemax_delta=|Qoffset_delta|.

Described below is a specific operation example of the method of usingthe criteria difference applied to the UEs having a CSG-ID in thewhitelist or the UEs registered in a CSG and the other UEs in the cellreselection, in deriving the maximum permissible power in hybrid cells.

FIG. 51 shows the outline of the process until the PRACH initialtransmission in hybrid cells in a case where the difference of cellreselection threshold is used.

First, the UE of a CSG member is described. In Step ST5101, the UE of aCSG member camps on a cell A after, for example, cell reselection. Thecell A transmits the broadcast information in Step ST5104, and the UE ofa CSG member receives the broadcast information. The broadcastinformation includes the cell reselection thresholds. In Step ST5105,the UE of a CSG member performs cell reselection process using, amongthe received cell reselection thresholds, the cell reselection threshold(S_intrasearchCSG) in a case where the UE has a CSG-ID in the whitelistor has been registered in a CSG. In Step ST5107, the UE determineswhether the cell reselection criteria are matched, and the UE proceedsto Step ST5109 in a case where they are matched or returns to StepST5105 in a case where they are not matched. In a case where the UE of aCSG member performs reselection to hybrid cell as a result of the cellreselection criteria being matched in Step ST5107, the UE camps on thehybrid cell in Step ST5109.

The hybrid cell transmits the broadcast information in Step ST5112, andthe UE of a CSG member receives the broadcast information. The broadcastinformation includes the maximum permissible power. Note that themaximum permissible transmission power to be broadcast in this case doesnot include the maximum permissible transmission power that is setdifferently for CSG member and non-CSG member as disclosed in thetwenty-second embodiment, and merely includes the conventional maximumpermissible power common to cells. In a case where uplink transmissionoccurs in the UE of a CSG member in Step ST5113, the UE proceeds to StepST5115, and derives the difference value (S_intrasearch_delta) betweenthe threshold value (S_intrasearch) for cell reselection in the casewhere the whitelist includes no CSG-ID and the threshold(S_intrasearchCSG) for cell reselection in the case where the whitelistincludes a CSG-ID. In Step ST5116, the UE of a CSG member takes thedifference value (S_intrasearch_delta) as a difference (Pemax_delta) oftransmission power for the UE of a CSG member and UE of a non-CSGmember, and derives the uplink transmission power (Pprach) using thedifference value (Pemax_delta) in Step ST5117. In Step ST5119, the UE ofa CSG member sets the uplink initial transmission power to thetransmission power and starts uplink transmission in Step ST5121.

Next, the UE of a non-CSG member is described. In Step ST5102, the UE ofa non-CSG member camps on the cell A after, for example, cellreselection. The cell A transmits the broadcast information in StepST5104, and the UE of a non-CSG member receives the broadcastinformation. The broadcast information includes the cell reselectionthresholds. In Step ST5106, the UE of a non-CSG member performs the cellreselection process using, among the received cell reselectionthresholds, the threshold (S_intrasearch) for cell reselection in a casewhere the whitelist includes no CSG-ID. In Step ST5108, the UEdetermines whether or not the cell reselection criteria are matched, andthe UE proceeds to Step ST5110 in a case where they are matched orreturns to Step ST5106 in a case where they are not matched. In a casewhere the UE of a non-CSG member performs reselection to a hybrid cellas a result of the cell reselection criteria being matched in StepST5108, the UE camps on the hybrid cell in Step ST5110.

The UE of a non-CSG member that has a CSG-ID in the whitelist but is anon-CSG member of the hybrid cell also has to perform reselection of ahybrid cell in an open access mode, and accordingly in the end, performscell reselection process using the threshold (S_intrasearch) for cellreselection in a case where the whitelist includes no CSG-ID, to therebydetermine whether or not the cell reselection criteria are matched. Inthe case of the UE that has a CSG-ID in the whitelist but is a non-CSGmember of the hybrid cell, for example, even though it initiallyperforms the cell reselection process using S_intrasearchCSG, the UE maybe configured so as to receive the CSG-ID of the cell and check theCSG-ID, and in a case where the CSG-ID is not matched, to perform cellreselection using the cell reselection process Step ST5106 for a non-CSGmember.

The hybrid cell transmits the broadcast information in Step ST5112, andthe UE of a non-CSG member receives the broadcast information. Thebroadcast information includes the maximum permissible power. Note thatthe maximum permissible transmission power to be broadcast in this casedoes not include the maximum permissible transmission power that is setdifferently for CSG member and non-CSG member as disclosed in thetwenty-second embodiment, and merely includes the conventional maximumpermissible power common to cells. In a case where uplink transmissionoccurs in the UE of a CSG member in Step ST5114, the UE proceeds to StepST5118, and in Step ST5118, derives the uplink initial transmissionpower (Pprach) using the conventional maximum permissible power(Pemax_common) common to cells that has been broadcast from the hybridcell in Step ST5112. In Step ST5120, the UE of a non-CSG member sets theuplink initial transmission power to the transmission power and startsuplink transmission in Step ST5122.

Note that the timing at which uplink transmission occurs differs foreach UE, and thus the timing of uplink initial transmission differs foreach UE. Accordingly, for example, Step ST5122 may be executedsubsequently to Step ST5121 as shown in the figure, or Step ST5121 maybe executed subsequently to Step ST5122.

As described above, it is possible to employ the method of varying themaximum permissible power used in deriving the uplink initialtransmission power in accordance with whether the UE camping on a hybridcell belongs to a CSG member or a non-CSG member, with the use of acriteria difference applied for the UEs having a CSG-ID in the whitelistor the UEs registered in a CSG and the other UEs in cell reselection. Inthis case, only the UE of a CSG member is allowed to increase thetransmission power for uplink transmission even when the UE of a CSGmember camps on the area that can be accessed, whereby it is possible tosecure the uplink received power sufficient for communications in ahybrid cell.

The methods disclosed in the seventeenth embodiment, the eighteenthembodiment, the nineteenth embodiment and the twentieth embodiment canbe used, not only limited to the specific example described above.

Not limited to the above-mentioned example, the PRACH initialtransmission power may be derived individually for the UEs of a CSGmember and the UEs of a non-CSG member based on the difference of thesetting parameters that affect the coverage size of a hybrid cell amongthe criteria for cell reselection.

Further, in a case where multiple criteria (for example, such asthreshold and offset for cell reselection) are set in cell reselection,which criteria are used may be determined in advance. For example,priority may be provided as to which criteria are used among multiplecriteria. This enables to use other criteria in the priority order evenwhen any of those criteria is not set. As another example, whichcriteria among multiple criteria are used in accordance with thedifference value thereof may be determined. For example, the criteriahaving the largest difference value are used. As still another example,an average value of the difference values of multiple criteria may beused.

Further, as another method, the serving cell may determine whichcriteria among multiple criteria are used and notify the UE of thedetermined criteria. As the notification method, the criteria may benotified as the broadcast information. The criteria may be determined bythe network side (such as MME and HeNBGW) not by the serving cell, andthen may be notified to the UE through the serving cell.

The interface S1 may be used in the notification to the serving cellfrom the network side. This enables flexible handling of an arrangementof cells including a hybrid cell. In a case where determination is madeby the network side, it is possible to set a value based on theenvironment of radio waves of neighbor cells and a load condition (forexample, such as the number of connected equipments). This enables toreduce the situation in which communications cannot be performed,connection delay due to erroneous communication, an increase insignaling amount, load concentration and the like, as a system.

The method described above uses the criteria in cell reselection.Accordingly, it is possible to use the method in a case where a hybridcell is reselected using the criteria. In other case, for example, in acase where the UE moves to a hybrid cell by HO, the method disclosed inthe twenty-second embodiment may be applied such that the setting valueis notified dedicatedly to the UEs that perform HO from the servingcell.

The method disclosed in the present embodiment enables to vary theinitial transmission power in starting uplink communication between theUEs of a CSG member and the UEs of a non-CSG member, whereby it ispossible to allow the UEs of a CSG member to stay longer at hybrid cellsthan the UEs of a non-CSG member.

Further, in order to enable the initial transmission power of the UE instarting uplink communication between the UEs of a CSG member and theUEs of a non-CSG member, the maximum permissible power used in derivingthe PRACH initial transmission power in the hybrid cell is providedindividually for the UEs of a CSG member and the UEs of a non-CSG memberand is notified from the hybrid cell to the UEs being served thereby.However, the maximum permissible power used in deriving the PRACHinitial transmission power in the hybrid cell is not required to beprovided individually for the UEs of a CSG member and the UEs of anon-CSG member, and accordingly does not need to be notified to the UEsbeing served. This enables to reduce the number of parameters requiredto be broadcast in the hybrid cell, and further reduce the informationamount for signaling.

The methods disclosed in the seventeenth embodiment to the twenty-thirdembodiment are applicable not only in a case (mixed carrier) where anopen mode cell (non-CSG cell) and a CSG cell coexist in the samefrequency carrier (same frequency layer) but also in a case (dedicatedcarrier) where only a CSG cell exists in the same frequency carrier(same frequency layer). In addition, those methods are applicable if ahybrid cell exists in the same frequency layer.

Further, those methods are applicable not only to the cell reselectionand HO in the same frequency layer (intra-frequency) but also to thosebetween the frequency layers (inter-frequency) or between systems (RATs)(inter-RAT).

While the LTE using a HeNB in which a CSG is used is described above,the present invention is also applicable to the UMTS using a HNB inwhich a CSG is used, a HeNB in which a CSG is not used, a HNB, and abase station having a small radius (also referred to as pico cell ormacro cell). The first modified example of the sixteenth embodiment iscapable of achieving the following effect in addition to the effects ofthe sixteenth embodiment. It is possible to reduce the power consumptionof the UE in a case where the UE has not been registered in the CSG celllocated in the vicinity of the present serving cell. Further, thesolution of the modified example of the sixteenth embodiment isexcellent in that the above-mentioned effect is achieved even if thenetwork side (such as a base station) does not recognize which CSG cella relevant UE is registered in (which CSG-ID is included in thewhitelist). As a result, the UE does not need to notify the base stationof the CSG-ID in the whitelist, which enables effective use of radioresources. Further, an effect that the processing load of a base stationis alleviated can be achieved in that the base station does not need tomanage a CSG-ID in the whitelist of the UEs being served thereby.

While the case where the CSG-ID that is the information broadcast by aCSG cell or cell and the tracking area code (TAC) broadcast by a CSGcell or cell are associated with each other is mainly described above,needless to say, the present invention is applicable even in a casewhere the CSG-ID and the TAC are not associated with each other.

In the case where they are not associated with each other, for example,whether or not registration has been made with the CSG and whether ornot the TA needs to be updated may be determined individually asdescribed below.

In the cell reselection, in a case of determining whether or not the ownUE has been registered in the selected cell, determination is made basedon whether or not the CSG-ID received in the broadcast information ofthe cell is included in the whitelist of the own UE. In the case wherethe CSG-ID received in the broadcast information of the cell is includedin the whitelist, it is determined that the own UE has been registeredin the selected cell. That is, it is determined that the cell can servea “suitable cell” for the UE. On the other hand, in a case where theCSG-ID received in the broadcast information of the cell is not includedin the whitelist of the own UE, it is determined that the own UE has notbeen registered in the selected cell. That is, it is determined that thecell is unable to serve as a “suitable cell” for the UE.

Further, in the cell reselection, in a case of determining whether ornot the TA needs to be updated, determination is made based on whetheror not the TAC received in the broadcast information of the cell isincluded in one or a plurality of TACs (hereinafter, TA list) stored inthe own UE. When the TAC received from the broadcast information of thecell is included in the TA list in the own UE, it is determined that theTA does not need to be updated and TAU is unnecessary. On the otherhand, when the TAC received in the broadcast information of the cell isnot included in the TA list in the own UE, it is determined that the TAneeds to be updated and TAU is required to be performed.

As a specific example, the above corresponds to, for example, StepST1406 to Step ST1409 of FIG. 14 or Step ST1607 to Step ST1610 of FIG.16.

INDUSTRIAL APPLICABILITY

While the LTE system (E-UTRAN) is mainly described in the presentinvention, the present invention is applicable to the W-CDMA system(UTRAN, UMTS) and LTE-Advanced. Further, the present invention isapplicable to a mobile communication system in which a closed subscribergroup (GSG) is introduced and a communication system in which anoperator identifies subscribers and the identified subscribers areallowed access as in the CSG.

The invention claimed is:
 1. A mobile communication system, comprising: a user equipment that performs handover from a closed subscriber group (CSG) base station that is a base station provided to a CSG cell belonging to a CSG to a base station provided to an other cell, or from the base station provided to the other base station to the CSG base station, wherein the mobile communication system varies a handover procedure between a case where the user equipment performing the handover is a CSG equipment belonging to the CSG and a case where the user equipment performing the handover is a non-CSG equipment not belonging to the CSG.
 2. The mobile communication system according to claim 1 wherein said CSG base station is a hybrid base station that allows access from the CSG equipment, and access from the non-CSG equipment.
 3. A method performed by a closed subscriber group (CSG) base station that is a base station provided to a CSG cell belonging to a CSG, from which a user equipment performs handover to a base station provided in an other cell, or to which the user equipment performs handover from the base station provided in the other cell, the method comprising: varying, by the CSG base station, a handover procedure between a case where the user equipment performing the handover is a CSG equipment belonging to the CSG and a case where the user equipment performing the handover is a non-CSG equipment not belonging to the CSG.
 4. A method performed by a user equipment, comprising: performing, by the user equipment, handover from a closed subscriber group (CSG) base station that is a base station provided to a CSG cell belonging to a CSG to a base station provided to an other cell, or from the base station provided to the other base station to the CSG base station; and varying, by the user equipment, a handover procedure between a case where the user equipment performing the handover is a CSG equipment belonging to the CSG and a case where the user equipment performing the handover is a non-CSG equipment not belonging to the CSG.
 5. A closed subscriber group (CSG) base station that is a base station provided to a CSG cell belonging to a CSG, from which a user equipment performs handover to a base station provided in an other cell, or to which the user equipment performs handover from the base station provided in the other cell, the CSG base station comprising: processing circuitry that varies a handover procedure between a case where the user equipment performing the handover is a CSG equipment belonging to the CSG and a case where the user equipment performing the handover is a non-CSG equipment not belonging to the CSG.
 6. A user equipment that performs handover from a closed subscriber group (CSG) base station that is a base station provided to a CSG cell belonging to a CSG to a base station provided to an other cell, or from the base station provided to the other base station to the CSG base station, the user equipment comprising: processing circuitry that varies a handover procedure between a case where the user equipment performing the handover is a CSG equipment belonging to the CSG and a case where the user equipment performing the handover is a non-CSG equipment not belonging to the CSG. 